1815.) On Iodine. 188 
tion, nor to infinitesimals, nor to vanishing quantities, nor even to 
limits except indirectly: that flusions, and variations which are also 
fluxions, ought to be taught among the very elements of geometry 
and algebra: that curves are most easily conceived and understood 
from their equations, not from the sections of solids: that the sec- 
tiqns of cones and of other solids may be very requisite in masonry, 
carpentry, civil and military engineering; but that the student of 
general science, without neglecting these sections, ought, soon 
after he knows the fourteenth proposition of Euclid’s second book, - 
and a little of algebra, to acquire the principles of fluxions, availing 
himself of that knowledge to render his progress continuous from 
Euclid through conics, which he will do by taking the equations to 
the ellipse, &c. from that to the eircle : and that, if such a method 
be followed, a diligent student will leave our Universities with a 
competent knowledge of Newton, Euler, Lagrange, Monge, La- 
place, and many others, and of any department of natural philo- 
sophy to which their mathematical researches are applicable. 
ARTICLE V. 
A Memoir on Iodine. By M. Gay-Lussac. 
(Concluded from p. 132.) 
Historical Note on the Discovery of Iodine. 
Ir was about two years after M. Courtois had discovered iodine 
that M. Clement announced it to the Institute on the 29th Novem- 
ber, 1813. M. Courteis had observed several of its properties, and 
particularly that which it has of forming a very fulminating powder 
when treated with ammonia. He intended to have ascertained all 
its properties; but being prevented by the attention required by an 
extensive manufactory of nitre, he engaged M. Clement to continue 
his researches. M, Clement, from similar motives, could only con- 
secrate to it a few moments. However, he obtained a great number 
of results, as may be seen by the note printed in the Ann, de Chim. 
Ixxxviii. 304. He discovered that by the combination of iodine 
and phosphorus a gaseous acid is obtained ; but he concluded from 
his experiments that this acid was composed of about 4 muriatic¢ 
acid and 4 iodine. M. Clement was employed in these experiments 
when Sir H. Davy came to Paris; and he thought that he could 
not better receive so distinguished a philosopher than by showing 
him the new substance, which he had likewise shown to MM. 
Chaptal and Ampere. I state these circumstances to answer a 
strange assertion which we find in the Journal of Messrs. Nicholson 
and Tilloch, No. 189, p.69:—** It appears that this gas (iodine) 
was discovered above two years ago ; but such is the deplorable state 
of scientific men in France, that no account of it was published till 
