PS 
Feb. 6,1873) 
ON THE OLD AND NEW LABORATORIES AT 
THE ROVAL INSTITUTION * 
Il. 
iG fal the next great name connected with our Institution, 
namely, Michael Faraday, of his life and his dis- 
coverics the history has been already written, so far indeed 
as it can be written, by Bence Jones, by Tyndall, and by 
Gladstone. Sz monumentum queris circumspice. These 
volumes of notes, from 1831 to 1856, will give some idea 
of the amount of work which he did in our laboratory; and 
their value will be better appreciated through the con- 
sideration that before these notes were made, no less than 
sixty of his scientific papers had been printed, nine of 
them in the “ Philosophical Transactions” 
_ Those of us who were present at Tyndall’s two memor- 
able lectures on “ Faraday as a discoverer” are not likely 
to forget the impression of the man left by them on our 
minds ; and for those who were not present it would be 
an office thankless to your lecturer and burdensome to 
his hearers, to contribute a feeble reproduction of those 
life-like memoirs, For our present purpose it will be 
sufficient to say that the entire fabric of those brilliant 
and manifold contributions to human knowledge was 
wrought out within the walls of the Royal Institution. 
His great experiments have been so often and so well 
exhibited in this theatre, that some apology is needed for 
bringing any of them before you again ; but in repeating 
for my own instruction some of those which bear more 
particularly upon the subject of Light, I have been 
tempted to reproduce one of them here. In doing this I 
I have been perhaps moved more by a fascination of the 
phenomenon, and by a piece of instrumental good fortune 
which enables me to introduce an old friend under a new 
garb, than by any better reason. The experiment in ques- 
tion is that which Faraday called “the magnetisation of 
light, and the illumination of the lines of magnetic force ;” 
we should now term it the rotation of the plane of polari- 
sation under the influence of the magnetic field. And in 
order that we may not even by inadvertence confuse the 
rotation here produced with that due to quartz, or oil of 
turpentine, I will draw your attention, by way of memo- 
randum, to the nature of the magnetism produced by 
spiral currents in given directions, and of the rotations of 
free currents produced by magnets. 
[The lecturer then showed the opposite rotations of 
two sparks discharged about the two poles respectively of 
an electro-magnet, and the reversal of those rotations, 
first by a change of the poles, and secondly by a reversal 
of the direction of the sparks. ] 
You now see upon the screen an image of the figures 
produced by a magnificent piece of heavy glass under the 
action of polarised light. Its size enables me to make 
use of about four times the amount of light usually avail- 
able in this experiment ; and I have taken advantage of 
the figure which its imperfect annealing produces, to vary 
the effect upon the screen. The dark parts of the figure 
indicate the parts of the beam in which the vibrations are 
perpendicular to those transmitted by either polariser or 
analyser, and which are consequently cut off. Now if 
anything should intervene to change the plane of those 
vibrations a portion of them will be! transmitted, and a 
partial illumination of the screen will ensue. This turn- 
ing of the plane of vibration is effected by the magnet as 
soon as its force is developed by the electric current sent 
through its coils. _ 
[The lecturer then “dispersed” the dark lines of the 
figure by means of a plate of quartz; and after turning 
polariser and analyser so as to colour the centre of the 
field with the tint intermediate between red and violet 
(teinte sensible), he showed that when the magnet was 
excited the field was rendered red or green according to 
the direction of the poles. ] 
* Continued from p. 224. 
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263 
Professor Frankland before coming to us had isolated 
the compound radicals Methyl, Ethyl, and Amyl, and 
had proved their resemblance to Hydrogen. Hehad also 
combined them with the metals zinc, tin, mercury, and 
boron. By this means he had obtained a very powerful 
chemical reagent, which proved of eminent service in sub- 
sequent operations. An instance of its power will be 
found in zinc— ethyl, which by its rapid combination with 
oxygen of the air, bursts into spontaneous combustion as 
soon as a flask containing it is opened. 
In conjunction with Mr. Duppa, Prof, Frankland 
worked in our laboratory at the artificial formation of 
ethers, They treated acetic ether with iodine and with 
the iodides of methyl, ethyl, and amyl; and by their 
means they arrived at a method for the formation of 
many organic substances which had previously been 
obtained only through the agency of animals or of 
vegetables. 
In 1866 Dr. Frankland determined by a long series of 
calorimetric experiments the maximum amount of force 
capable of being developed by given weights of the diffe- 
rent foods commonly used by men. 
In the following year he investigated the effect of pres- 
sure (up to 20 atmospheres) upon the luminosity of flames 
of hydrogen and of carbonic oxides. He found that these 
flames, so feebly luminous at ordinary atmospheric pres- 
sure, burn with brilliant light under pressures of from 10 to 
20 atmospheres, and that the spectra of these brilliant 
flames are perfectly continuous. From the latter circum- 
stance he infers that solar light may be derived from 
glowing gas and not from incandescent solid or liquid 
matter. 
As these researches have so important a bearing upon 
spectral analysis and solar physics, I will venture to re- 
peat one or two of the experiments. Here are three 
closed tubes filled respectively with hydrogen, oxygen, 
and chlorine, at atmospheric pressure. The densities of 
these substances are in the proportions 1: 16: 354; and 
if the spark from an induction coil be made to pass 
through them, the luminosity of the discharge will be 
found to be nearly in the same proportions. That this 
result is really due to the density, and not to the chemi- 
cal constitution of the gases, may be proved by allowing 
the discharge to pass through this tube, and by pumping 
air into it during the discharge. It will then be seen that 
the brilliancy increases with the pressure. 
These researches were suggested by an old experiment 
of Cavendish’s, in which he exploded a mixture of oxygen 
and hydrogen, first under atmospheric pressure and then 
under a pressure of from 10 to 12 atmospheres. In the 
first case there is much noise and little light; in the 
second, a brilliant flash and no noise. The labours of 
Dr. Frankland have rendered this experiment intelligible, 
and have correlated it with other phenomena. 
Of Dr. Frankland’s successor, Dr. Odling, I should 
have had more to say, had he not been attracted by a 
well-deserved offer of the chemical chair at Oxford. As 
a member of that University I rejoice at the appoint- 
ment, while here we regret the loss. 
Of Faraday’s successor, John Tyndall, I am greatly at 
aloss howto speak. In this place his presence seems so 
near to us, his thoughts so subtle, his words—even when 
rung back to us from those busy cities far away on the 
other side of the Atlantic—so familiar and yet so stirring, 
that it behoves us that ours should be wary and few. 
Few men have brought so large a burden and bulk of 
contribution to the common stock of knowledge ; but still 
fewer have inspired in his hearers so strong a love, such 
ardent enthusiasm for the subjects of his research. 
' It is now twenty years since Prof. Tyndall began his 
researches in our laboratory. During the first thirteen 
years he produced no less than thirteen papers, which 
were printed in the “ Philosophical Transactions :” on 
Sound, on Diamagnetism, on Glaciers and Ice, on the 
