152 Prof. A. de la Rive’s Memoir of 
It is easy to understand all the importance of an investigation 
the result of which was to modify completely, the received ideas 
as to the constitution of the permanent gases by causing them 
to enter into the category of simple vapors; this was to intro- 
duce into molecular physics a new and important notion, the 
consequences of which have gradually unfolded themselves. 
It is also to a question of molecular physics that we must 
refer the memoir on the relations of gold and the other metals 
to light, published by Faraday in 1857. Among other interest- 
ing facts that this memoir contains, we shall cite that of a leaf 
of beaten gold, which, when p. laced upon a plate of glass, be- 
comes perfectly transparent and colorless when it is brought to 
a high ee and which, when seen by transmitted baa 
tigation of the various colors shale’ we different solutions 
of gold, and especially of the fine ruby-red tinge obtained by 
the solution of a quantity of gold which, if agglomerated into 
a single mass, would not occupy the seven-hundred- thousandth 
part of the volume of water which it colors. It is not neces- 
sary to dwell upon the interest presented by researches having 
for their object the study of the influence, still so imperfectly 
known, of the molecular structure of bodies se their relations 
to light, and especially upon their transparen 
ng the numerous works of Faraday rélatioe to the appli- 
eations of science to the arts, we shall confine ourselves to ci- 
ting his researches —— the manufacture of steel, and of glass 
for optical purposes, these being the most important. 
It -was by the se ae of the Indian steel called wootz that 
he was led, in concert with Stodart, to compose an alloy which 
had all the ee of this, by combining aluminium wi 
iron and carbon. Ina letter addressed in 1820 to Professor 
De la Rive,* he relates all the attempts Sone by his collabora- 
teur and himself during two years of persevering labor, to dis- 
cover the most satisfactory alloys. He indicates, as one of the 
* See Bibl. Univ. (1820), vol. xiv, p. 209. 
| 
: 
