SCIENCE. 
i5 
method of receiving at B the illumination of the little 
squares at A.” 
Even this plan appears to have been anticipated 
in one sense two years ago, by Mr. J. E. H. Gordon of 
London, who says : 
“ I used an electromagnet consisting of an iron bar 
2 feet 4 inches long and 2J inches in diameter, sur- 
rounded by 70 lbs. of wire, and excited by ten Grove 
cells. 
The total double rotation produced, not by slightly 
altering the resistance, but by reversing the current, 
was never more than 26' (twenty-six minutes of 
arc). 
To see this at all with a very delicate Jellett analy- 
zer, it was necessary for the observer to increase the 
sensitiveness of his eye by sitting in total darkness 
for some ten minutes before each observation. 
Your readers can judge what chance of obtaining 
visible changes of illumination there would be with 
‘ little ’ magnets and mere variations in a current not 
powerful enough to fuse a selenium resistance.” 
Lastly we may offer an apparatus arranged by Mr. 
Middleton of Cambridge, England, who gives the 
following account of it : — 
“ A lens is used to throw on a plane or suitably 
curved receiving plate (inclosed in a camera) the 
image of any object. The receiving plate of the 
camera is composed of thermopile elements, ground to 
a smooth surface, and having their posterior faces put 
in electrical communication by a system of wires, 
with a somewhat similarly constructed plate. The 
heating, &c., effect of the image on the first plate gen- 
erates currents of electricity, which flow through the 
wire system, and on reaching the second thermopile 
plate are reconverted into heat, &c., according to the 
law discovered by Peltier, the amount of heat, &c., 
being directly proportional to the amount of elec- 
tricity. 
Moreover, according to the manner in which the 
elements of the plate are arranged with respect to 
each other, we can get a ‘ positive ’ or ‘ negative ’ 
(to use the ordinary phraseology of photography) pic- 
ture on the second receiving plate, since the Peltier 
effect here holds, and the copy of a picture depends 
solely on establishing a constant ratio in the radiant 
heat and light which corresponding points of the 
picture and copy send to the eye. 
Furthermore, these images can be either viewed 
directly or by reflected light (after the fashion of the 
the Japanese mirrors and projection on a screen), or 
by suitable apparatus they can be retained as a 
photograph, a thermograph, or chemicograph, the de- 
tails of which will be found in the paper alluded to, 
and of which an abstract will, I believe, soon appear 
in the Proceedings of the Cambridge Philosophical 
Society. Also, I touched upon the method of attack- 
ing the problem of photographing in colors, and in 
conclusion pointed out a striking anology between the 
camera of the instrument and that of the human eye ; 
the thermo-electric elements of the instrument and the 
rods and the cones of the eye ; the conducting system 
of insulated wires emanating from the plate of the in- 
strument and the optic nerve (or bundle of conducting 
fibres of the eye) — supposing that as the electric cur- 
rents in the instruments effected a registration on the 
sensitive paper, so in the eye the nerve currents of the 
optic nerve probably leave some brain trace on the 
mind.” 
It will thus be seen that while “ seeing by tele- 
graph ” is not by any means a new invention, the 
principle involved is one full of interest, and as yet 
but partially developed ; in this field of research ample 
scope will be found for those working in this direction 
and valuable results may be anticipated. 
THE COMING OF AGE OF THE ORIGIN OF 
SPECIES. 1 
Many of you will be familiar with the aspect of this small 
green-covered book. It is a copy of the first edition of the 
“ Origin of Species,” and bears the date of its production — 
the first of October, 1859. Only a few months, therefore, 
are needed to complete the full tale of twenty-one years 
since its birthday. 
Those whose memories carry them back to this time will 
remember that the infant was remarkably lively, and that a 
great number of excellent persons mistook its manifesta- 
tions of a vigorous individuality for mere naughtiness ; in 
fact there was a very pretty turmoil about its cradle. My 
recollections of the period are particularly vivid ; for hav- 
ing conceived a tender affection for a child of what appeared 
to me to be such remarkable promise, I acted for some 
time in the capacity of a sort of under-nurse, and thus 
came in for my share of the storms which threatened even 
the very life of the young creature. For some years it was 
undoubtedly warm work, but considering how exceedingly 
unpleasant the apparition of the new-comer must have 
been to those who did not fall in love with him at first 
sight, I think it is to the credit of our age that the war was 
not fiercer, and that the more bitter and unscrupulous 
forms of opposition died away as soon as they did. 
I speak of this period as of something past and gone, 
possessing merely a historical, I had almost said an anti- 
quarian, interest. For, during the second decade of the ex- 
istence of the “ Origin of Species,” opposition, though by 
no means dead, assumed a different aspect. On the part 
of all those who had any reason to respect themselves, it 
assumed a thoroughly respectful character. By this time 
the dullest began to perceive that the child was not likely 
to perish of any congenital weakness or infantile disorder, 
but was growing into a stalwart personage, upon whom 
mere goody scoldings and threatenings with the birch-rod 
were quite thrown away. 
In fact, those who have watched the progress of science 
within the last ten years will bear me out to the full when I 
assert that there is no field of biological inquiry in which the 
influences of the “ Origin of Species ” is not traceable ; the 
foremost men of science in every country are either avowed 
champions of its leading doctrines, or at any rate abstain 
from opposing them ; a host of young and ardent investiga- 
tors seek for and find inspiration and guidance in Mr. Dar- 
win’s great work ; and the general doctrine of Evolution, to 
one side of which it gives expression, finds in the phenomena 
of biology a firm base of operations whence it may conduct 
its conquest of the whole realm of nature. 
History warns us, however, that it is the customary fate 
of new truths to begin as heresies and to end as supersti- 
tions ; and, as matters now stand, it is hardly rash to antici- 
pate that, in another twenty years, the new generation, edu- 
cated under the influences of the present day, will be in 
danger of accepting the main doctrines of the Origin of 
Species with as little reflection, and it may be with as little 
justification, as so many of our contemporaries, twenty 
years ago, rejected them. 
Against any such a consummation let us all devoutly 
pray; for the scientific spirit is of more value than its pro- 
ducts, and irrationally-held truths may be more harmful 
than reasoned errors. Now the essence of the scientific 
spirit is criticism. 1 * tells us that to whatever doctrine 
claiming our assent, we should reply, take it if you can 
compel it. The struggle for existence holds as much in the 
1 A Lecture delivered at the Royal Institute, Friday, March 19. 
