ADDRESSDELIVERED BEFORE THE MEMBERS

OF THE

WEST KENT NATURAL HISTORY, MICROSCOPICAL,AND PHOTOGRAPHIC SOCIETY,

BY

The President, W. G. LEMON, Esq., B.A., LL.B., F.G.S.

ON THE 23rd FEBRUARY, 1881.

Gentlemen,

The Report presented to you this evening by the Council

deals so concisely, and so fully mth the work done by the Society

during the past year, that nothing remains to be added by me to

the particulars thus laid before you. I am deeply conscious of the

honour conferred upon me by electing me your President ; and

when I call to mind the illustrious scientific workers who have

preceded me in this chair, I know that the oflfice is accorded me,

rather by your indulgent kindness and goodwill, than on account of

any merit of my own.

The year has not been without signal advances, we may say

triumphs, in almost every department of science. Explorations in

Thibet, in Africa, and the ice-bound polar regions—manifold im-

provements in mechanics, metallurgy, and electrical science—geo-

logical investigations in our own County (especially those of Mr.

Flaxman C. J. Spurrell, a worthy son of one of our most honoured

members, and himself a member, I may say an alumnus, of this

Society) ; all claim attention. But when the history of 1880 is

written, it will be found that " Light " has occupied very much

of the time and thought of scientific observers.

The connection of light with heat, and with some forms of

chemical action, has been long admitted as a fact, and some of its

influences on living organisms have been carefully noted. By the

scientific progress of recent years the question is forced into promi-

nence, "What is the relaticm between light and electricity?" Werecognize in light a form of energy or force, but of its intimate

nature we know scarcely anything. We speak of it as the dis-

turbance of some medium, such disturbance being periodic, both

10

in space and time ; and we explain many of its physical phenomena

by adopting the theory of undulatory or wave-like motion. Of

electiicity we are still more ignorant ; we cannot even assert it

to be a form of energy ; and yet we have had demonstrated to

us during the past year some very marvellous results produced on

organic life by the action of what is known popularly as the electtic

hght. We appreciate the results, but the complete elucidation of

the "how'' and the "why" has yet to be attained.

The old satirist spoke with undisguised contempt of the

scientific experimentalists of his day, laughing at them as essaying

to extract "sunbeams fi'om cucumbers;" but now vegetable or

carbon points diffuse a light having many of the qualities pos-

sessed by sun-light. Sober men of science look upon trees and

plants as incorporating -within themselves the sun-light and heat

of to-day; while our coal fires, with their unconsumed smoke

and their fog-creative activities, represent the imperfectly liberated

sunbeams of prehistoric ages, warming our houses but eclipsing

our present sun.

It has been long known, that vegetable organisms are to a great

extent dependent upon the direct influence of light for vigorous and

healthy development. The extreme sensitiveness of some plants

to the action of light has been clearly shown in a paper recently

read before the Linnean Society by Mr. Francis Darwin, on" "The

power possessed by leaves of placing themselves at right angles to

incident light." As an illustration, he took cotyledons of the

seedling radish. "When the plant is illuminated fi-om above the

cotyledons are extended horizontally, being thus at right angles

to the light falling upon them. If the seedling is placed at a

window, so that it is lighted obliquely from above, and if the stem

(hypocotyl) is prevented from bending, the cotyledons will accom-

modate themselves to the changed conditions by movements in a

vertical plane. The cotyledon which points to the light will sink,

Avhile the other will rise, until both are once more at right angles

to the incident light. Two different theories have been suggested

to account for this property in leaves. One by Frank, who

ascribes to leaves and some other organs a specific sensitiveness

to light, which, for simplicity's sake, he calls Transversal-heliotro-

pismus; the other by De Vries, who thinks the effect is produced

by the ordinary forms of heliotropism nnd geotropism acting in

11

concert. Mr. Darwin inclines to the first of these explanations.

I do not propose to discuss theories, but call your attention to

tliese and similar facts; and would suggest to our younger mem-bers that they should read Mr. Darwin's book on " The Power of

movement in Plants," as giving them much information presented

in an agreeable form.

M. A. Pauchon has conducted a prolonged series of experi-

ments to ascertain the influence which light has on the ger-

mination of seeds. Failing to obtain satisfactory results by

the direct method, he compared the respiratory activity of seeds

under different conditions of light and obscimty, measuring this

activity by their absorption of oxygen. Taking identical parcels

of seeds of equal number and equal weight, he arrived at the

following conclusions :

—

1. Light constantly accelerates the absorption of oxygen by

gcrmiuating seeds. The advantage in favour of light varies from

a quarter to one-third of the amount of oxygen absorbed by the

seeds kept in the dark.

2. There is a relation between the degree of illumination and

the amount of oxygen absorbed. The influence of light is very

manifest under a clear sky and bright sun ; with a cloudy sky it

gradually decreases.

3. The acceleration produced by exposure to light continues

for some hours after the seeds are placed in the dark.

4. The difference in quantities of oxygen absorbed in light

and darkness are greater in winter than in summer. Hence it

would appear that the influence of light upon this respiration is

more intense at low temperatures.

Professor Pringsheim, by concentrating solar light on vege-

table tissue under a microscope, finds that the absorption of oxygen

increases with the intensity of light, and especially vnth the

intensity of the chemical rays. But the increasing intensity of

respiration involves danger to the vegetable tissue ; and the light

which is necessary for accumulating carbon becomes hurtful as soon

as oxidization exceeds power of assimilation. Chlorophyll, by its

luminous absorption, helps to balance these two functions ; by

its preference for chemical rays, it diminishes the respiratory

effort, and thus acts as a protecting screen or regulator of respi-

ratory action.

12

It has been stated that gardeners in the Azores have noticed

the deTelojDmeut of buds of roses to be quickened by the admission

of smoke into the conservatories. If this be so, one must suppose

that the smoke employed is wood smoke, consisting entirely of

particles of carbon or vegetable ash, and not the Impure smoke

which Avould be found in our conservatories, heated by coke or

coal.

Thus far our observations i-efer to sun-light ; but perhaps the

most remarkable observations of the year are those made in deter-

mining the effect of the electrical light upon plants. For these we

are indebted to Dr. Siemens, F.R.S., who conducted his experi-

ments in this county near Tunbridge Wells.

It is well known that chlorophyll (the green colouring matter

of leaves), starch, and cellulose, are developed in plants by the dis-

sociation of carbonic acid and water in the cells of leaves. The

power in nature which sets this decomposition in motion is sun-

light, and the question suggests itself, Is this power confined

entirely to sun-light? Sun-light contains «c/m/s/« ,- so does the

electric light ; and experiments show that the actinic rays in sun-

light play an important part in ripening grain and ftniit. Dr.

Siemens proposed to try whether a similar effect would be pi'oduced

by electric light, i.e., whether such light might be ad^-antageously

employed in aiding or supplementing sunshine in the growth of

plants, shrubs, fruits, and flowers. Our climate has not too many

hours of sunshine, and it would be a boon to the gardener to find

means of artificially gaining some of the benefits of sunshine.

With a two-horse power engine and a dynamo-electric machine,

Dr. Siemens was able to produce a light equal to 1400 caudles. By

means of a reflector fixed in the open air, he directed this light

upon a sunk melon house. Pits were prepared with mustard,

cress, carrots, cucumbers, and melons ; and were di\ided into four

groups. 1 . Was kept entirely in the dark. 2. Was heated Mith

electric light exclusively. 3. Was exposed only to daylight. 4.

Had both dayhght and electric light, the latter from 5 to 11 p.m.

The results were :— 1 . Plants yellow, soon died. 2. Plants fight

green, pretty strong leaves. 3. Leaves of ordinary colour and

strength of daylight growth. 4. Plants had more strength, and the

gi-een was remarkably rich and dark. The next step was to place

the electric lamp in the same glass house with the plants. Here

13

they were exposed to the electric light for Bix successive nights,

beginning when daylight failed, and continuing till sunrise. Theplants had thus no rest, but they did not suffer. The experiment

was next tried in the open air, with successful results, and the

invigorating effect of electric light and sun-shine combined was

very marked.

It still remained to be seen whether the electric light would

aid in ripening fruit. Dr. Siemens therefore tried its effect ujjon

strawberries. He took two pots of strawberries started under

precisely similar conditions. One was exposed to dayhght only

in the usual way, and showed a bunch of green berries ; while the

other which, in addition to daylight, had been under the electric

light during the night, bore a cluster of ripe, large, well-flavoured

berries. Thus demonstrating that electric light promoted the

formation of the saccharine and aromatic substances on which the

ripening and flavour of fruit depend.

While we have thus spoken of light as affecting the life and

growth of plants, we must not forget that there are some species

of fungi which may be classed as light-giving. One of the best

known of such species is the Agaricus olmrius, which was someyears since the subject of a monograph by Tulasne, published

under the title " Sur la Phosphorescence de Champignons," (Ann.

des Sci. Nat., vol. ix. p. 338). At first it was conjectured that

such phosphorescence was developed ot^ly at the time of decompo-

sition ; but further obseiTations have so far changed this opinion

that now some assert the fungus is phosphorescent only during

growth ; that when it ceases to gTow, it ceases to shine. This light

is of a pale bluish colour resembhng that emitted by phosphorus

in a dark room.

Let us now turn to the animal world and briefly trace some

of the influences of light upon its members.

By far the larger number of animals are conscious of light by

means only of the eye. There are but few back-boned animals

absolutely without eyes. Moles, the Proteus, and the blind fish,

as they are called, of the American caves {Amhlyopsis Spelcens,

etc.) have all rudimentary eyes; and in most ca.ses the condition

of the eye in such animals is one of degeneration, the development

of the organ being arrested at an almost embryonic stage; while,

as the animal attains maturity, the eye being small, deeply im-

14

bedded in muscles, and quite covered mth the external skin, is

not easily detected. True eyeless fishes have been hitherto found

only at great ocean depths, and we are indebted for our knowledge

of them to the "Challenger" expedition. Many of these eyeless

fishes have on the head peculiar and sometimes very large organs

which have displaced the eyes. These may, according to Dr.

Giinther, be strongly developed phosphorescent organs; while

the non-bHnd fishes of the deep ocean have exceptionally large

eyes, which seem fitted to absorb pale phosphoric light. Sir

Wyville Thomson thinks these large eyes have become exagge-

rated, to enable the fishes to catch the feeble rays of light coming

from above; although he acknowledges that, so far as he can

judge, direct sunlight does not penetrate to gi'eat depths. While

admitting that abyssal creatm-es are phosphorescent in their native

depths ; he regards as untenable the notion that any deep sea

animals see by the phosphorescent light emitted by thousands of

their neigbbours.

The struggle for existence goes on as well in the dark silent

depths of the great ocean as in the busy whirl of civilized Ufe, and

in the shades and glens of primeval forests; and we can thence

conjectiu-e how these diverse organs, to which we have referred, are

mutually related. The lights which the blind fishes carry in their

two lanterns on their heads may serve at the same time to attract

their prey, and possibly give help to fishes who can see. Every

form having small eyes or small illuminating organs, being unable

to gain food, would be exterminated ; while none but the extremely

developed species would hold their own in the struggle. This

suggestion implies that the lantern-fishes of the deep sea being

bhnd, must have other means of distinguishing friend from foe,

and of identifying their prey. Such appears to be the case, for

from their proboscis or muzzle hang long feelers, beards, and the

like, at the tips or bulbous ends of which organs of sense or touch

may probably be situate. This matter has yet to be more fully

investigated ; and such inquiry is rendered more difficult by the

fact that, owing to the conditions of life at great depths, and pos-

sibly also to the mode of collecting specimens, the animals

brought up were all dead before reaching the surface.

Though truly blind vertebrates are rare, eyeless invertebrates

'

are far more numerous. In some parts of the Continent of

15

Europe, nnder huge boulders, wheie liglit can never penetrate, are

found fauna specially adapted to such conditions of life ; blind

spiders, beetles, etc., occur in such positions. Many ento-parasites

are eyeless, and this fi-om their habitat we might expect to be

the case ; some have only rudimentary eyes. The number of

known species of blind cave insects amounts to hundreds.

Associated with these we find blind spiders, Crustacea, and

Myriapoda. The so-called blind crab of the Kentucky caves

is said to have rudimentary eyes; whilst other Crustacea (as Stygia,

Titanethes alhus, etc.), seem to be totally bhud. A list of these,

with illustrations, is given in the work of Putnam and Packard on

the Mammoth Cave of Kentucky. The " Challenger " expedition,

and the literature in relation thereto, will afford additional illus-

tration of the large number of blind invertebrates. Totally blind

crustaceans were found Uving at a depth of over 2000 fathoms.

While darkness so complete as to prevent all use of the eye as an

organ of hght has led to the degradation of its structure, we should

be guilty of too hasty generalization, if we should hence formulate

a law that lack of light must necessarily lead to total or partial

blindness. Insects having weU-developed eyes are found inhabit-

ing the same spots as blind insects. Dr. Semper says that in some

caves in the Philippines and Pelew Islands, which he had personally

explored, he found in spots where absolute and total darkness

reigned, only insects tvith eyes. Again, it is known to most ento-

mologists that in all species of the cave beetle Machmrifes, the

females only are blind, while the males have well-developed eyes,

yet they live together in absolute darkness. I have not been able

to ascertain whether or not, at certain seasons, the female becomes

phosphorescent ; if this be so, it might help to account for the

sexual difference. These facts would appear to show that total

blindness in a particular species may arise from causes other than

absence of light alone.

Enough, perhaps, has been said with reference to the special

organs of sight. "We have ah-eady intimated that in light we have

something more than a luminous energy. Sun-light has its heating

and its chemical powers, and these affect the animal as they do the

vegetable organism. Animals in general breathe with less intensity

in the dark than in the light ; at all times they are burning carbon,

but the activity of its consumption is greatest in the light. Light,

16

too, as we have seen in the case of plants, acceleiates the nutrition

and development of animal life. If the eggs of a frog be placed in

two glasses of water, one transparent and the other covered so as

to be impermeable to light, it -nill be found that in the first the

eggs wiU develop naturally, while those in the dark will develop

very slowly, and not advance fui-ther than rudimentary embryos.

Similar results will be obtained by placing the eggs of the common

house fly in glasses of different degrees of transparency or colour.

Placed simultaneously in various coloured glasses, insects of

different degi-ees of development will be produced. In an experi-

ment it was found that while all the eggs were hatched, the insects

in blue glasses were by far the most developed ; in gi-een they

were the smallest ; whilst in the red, yellow, and white were pro-

duced insects of ordinary size. Adult animals, too, are affected by

the colour of light. The effect of red light on the amount of

carbonic acid during respiration is well known.

A word or two as to the effect of light in the formation of

colour in the skin. Formerly it was accepted without question that

all animal colouring was caused by the direct influence of light upon

the skin. Xow it has been clearly established by experiment that in

the tadpoles of common toads and frogs, the pigment is equally well

developed in total darkness, as in yellow, blue, or red light ; and the

development of pigment cells would seem to depend on influences

other than those arising from mere luminous rays. Such develop-

ments may be more closely connected with the heat producing, or

the chemical, not to add the electrical, influences associated with

sun-Hght. The theory of natural or sexual selection which is so

often used to account for differences in colour, would at fu-st sight

appear to be in antagonism to this suggestion ; but a careful con-

sideration will, I think, show that so far from this being the case,

the suggestion is supplementary only to the Darwinian principle.

Man himself is conscious of the physical effect of bright sun-

shine; in addition to the beauty with which the sun in its glory

gilds aU nature, and paints the flowers, it wakens songs of joy in

the birds, and causes our own blood to flow with greater activity,

stimulating us to exertion and augmenting our enjoyment of life

itself. It is true all animals are not affected in the same way by

alternations of light and darkness. Some go to rest as night

approaches, others rouse themselves and go forth to seek their

17

prey. These diurnal and nocturnal species will he iound scattered

among maiunials, birds, and insects; they are, however, so un-

important and few in number as not seriously to affect the truth

of the general principle that liffhf jjromotes life.

The perfecting of the electric light and the means of so

dividing its current as to enable the light to be used in domestic

life, is not uninteresting considered with reference to life and

health. It may thus, at some future day, be possible for our

descendants to obtain an illuminating agent free ft'om the yellow

glare of our ordinary artificial light ; to live in well lighted rooms

free from the sulphurous and poisonous vapours, now so liberally

supplied by gas companies together with their gas, and to breathe

during the evening working hours an unburnt and purer

atmosphere.

Our Society concerns itself with Photography, and we were,

in April, favoured with a very interesting Paper on " Photo-

graphy," illustrated by experiments. Mr. Webster produced

some examples of instantaneous photographs, and very fully

described the advance made in the science of photography owing

to recent improvements in the gelatine method. At our summer

meeting, notwithstanding the weather was very wet and the sky

leaden, he succeeded in taking a very admirable and sharp nega-

tive. The plates are now made so sensitive that the exposure is

of very short duration. An express train passing at full speed

through Chislehurst, on its way to Dover, has been jAotographed.

The " Flying Dutchman" was photogi'aphed as it passed through

Twyford Station at a speed of sixty miles an hour. All the details

of the engine were distinctly pourtrayed, although the exposure

could not have been more than a fraction of a second. The

rapidity of photographic action is more marked by the photo-

graphing of a lightning flash by its own light, recently accom-

plished by Mr. Crosse, of Liverpool. "With his camera, situate at

Dingle, he succeeded in getting an excellent portrait of a long

zig-zag flash, which leapt out from a cloud over St. Philemon's

Church at the moment the bell tower was rent in pieces.

Experiments patiently continued have resulted in the dis-

covery of means of obtaining positive photographs which retain,

in some degree, the colour of the objects photographed. The

process is yet in its infancy, and the specific materials used in the

composition of the sensitive medium are not made known.

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The photophone, although not strictly within the range of

subjects hitherto considered by our Society, is yet so intimately

connected mth the topics now under notice, that a passing refer-

ence must be made to this very wonderful invention. Mr. Graham

Bell has the honour of being the first to make known the remark-

able effects produced by this instrument. By its means sound is

conveyed, not by a string or wire, but by a beam of light. Aplain bright flexible mirror is fixed on a stand, the light thrown

upon it as a beam is reflected so as to strike a parabolic reflector

placed at a distance. In the focus of the parabolic reflector is

placed a cell of silenium connected with a galvanic battery and a

telephone. If a voice speak behind the flexible mirror vibrations

are produced, and these are communicated to the beam of light,

and the vibrations acting along the light produce a sound which

becomes audible by the telephone. It has been long known that

various metals and metalloids give sounds under the action of

light and heat; and, in addition to silenium, it is asserted that

gold, silver, platinum, iron, steel, brass, copper, zinc, lead, and

even paper, parchment, and mica are sensitive to light vibrations.

Mr. Shelford Bidwell also succeeded in constructing a photo-

phone, differing in some respects from that of Mr. Graham Bell.

The transmitter is a thin disc of mici'oscopic glass silvered on its

anterior surface, and placed in front of a tube, by which the voice

is conveyed to it so as to excite vibration. The lime, or electric

light, is reflected fi'om this mirror through a con^-ex lens so as to

render the rays parallel ; these being received on a second lens at

some distance, and again concentrated on a silenium receiver.

The voice is conveyed across a space of ten feet into a neighbouring

room by this instrument. While experimenting with the photo-

phone the thought occurred to him that an instrument might be

constructed to transmit pictui'es of natural objects by means of

the electric current. Thus he would be able to telegraph not

merely symbols but actual portraits, and take a photo-picture

many miles from the object. He has so far succeeded as to show

that the problem is certainly not insoluble. A description of his

process, and of the instrument employed, is given in Nature, Feb.

10, 1881. Every one reading his account of his work must very

heartily wish that this pains-taking and accomplished physicist maybe successful in developing to perfection what he calls " Tele-

photography."

19

As connected with liglit, I may remind you of the splendid

manifestation of the " Aurora Borealis " on the evening of Thurs-

day, January 31 last. Standing on Blacklieath, I witnessed the

pulsations of the aurora reaching to the zenith, and shedding a

brilliant light over the heavens.

Leaving now matters connected with light, I pass on to notice

two topics of local interest which may possibly deserve a record

amongst us.

None of us, probably, have ever seen so severe a snow-storm

as that which visited not only bur own locality, but the whole of

the eastern and central parts of Great Britain on Tuesday, Jan-

uary 18th, 1881. A strong wind of almost unexampled fierceness

drove the snow from the north-east in such abundance, and heaped

it in such drifts, as soon to render roads impassable. In some

parts of Blackheath the snow was from ten to twelve feet deep,

while the road between Loampit Hill to Lewisham was in parts

covered with snow fourteen feet deep. The railway cutting

near St. John's was so filled with snow that no train was able to

get through after early in the afternoon ; the next day the traffic

on the Mid-Kent line continued to be suspended, and several days

elapsed before matters were restored to their usual condition. Theroads were with great difficulty cleared to enable communication

to be maintained between the different parts of the district, a snow

plough being used for the pm'pose. A heron is reported to have

been found frozen to death in the neighbourhood of Forest Hill.

While earthquakes have disturbed other lands, and the inha-

bitants of Northwich, in Cheshire, have found the ground giving

way beneath them, and the River Bradford, a tributary of the

Don, has been lost to the inhabitants of Alport, in Derbyshire, our

own usually quiet Blackheath has suffered some alarms. In the

beginning of November, 1880, a small irregular shaped hole, about

18 feet in circumference, appeared near the gravel pit lying to the

north of Eliot Place. The sides of this hole were perpendicular

on the north and south, but on the south-west and south-east the

ground retreated as if leading to some excavation or large cave.

An examination made at the time showed, however, that no

further opening could be traced. It was generally considered that

this hole was of the same nature as one which occurred in April,

1878, near the centre of the Heath, to the west of the spot where

20

the roatl ft-om Maze Hill to Montpelier Row crosses that from

Shooters' Hill to the west corner of Greenwich Park. On the 19th

of November, 1880, another subsidence was observed, the spot being

about 100 yards south-east of that where the subsidence occurred in

1878. This new hole was about 18 feet deep, cylindrical mthvertical sides, Uke a well. Some of the residents desire either by

sinking a shaft, or by excavating at this spot, to endeavour to find

what are the causes of these subsidences. The Heath is a small

table land, and it is well Icnown that the sides of the slopes leading

up to its surface at Maze Hill and Grooms Hill, contain caves which

were formerly used by men, who in the good old times occupied

themselves in various modes of conveyancing and transfer of pro-

perty. Some persons have expressed an opinion that these indus-

trious persons had large subterranean stables, in which they kept

their horses ; and extensive galleries beneath the surface, used

by them for storage of the goods they held, not in trust for

the former owners, and the value of which to themselves might be

affected by exposure to day-light. Other persons have valuable

traditional knowledge of an underground passage leading from

Greenwich to Eltham, constructed in the times of King John, of

Magna Charta memory. All these statements and traditions

need verification, and until they are substantiated, or more pro-

bable evidence in their support adduced, those of us who reside

on the borders of the Heath may sleep peaceftilly in our beds

;

not fearing that the anticipations of the newspaper writers will

be fulfilled by our residences sinking bodily into mother earth.

Speaking generally, the surface of the Heath consists of a crust

of " Blackheath gravel," varying in thickness, but believed to be

about fifty feet thick, and thinning out towards Lewisham and

Lee. Beneath this underlie beds of shelly clays, associated on the

west and south-west with fine sands, probably in some parts forty

feet thick ; beneath these are the Thanet sands, estimated to be

from forty to fifty feet thick ; then we come to the chalk formation,

which forms the escarpment between Woolwich and the entrance

to the Ravensbourne valley, and is seen cropping up near St.

John's. By some it is thought that these holes are old excavations

for obtaining gravel and sand, which have been filled up but not

sufficiently rammed, and that after heavy rains the earth in them

has consolidated. I am inclined t<i think they are over the sites of