482 



Having now performed this, the most agreeable duty of a Presi- 

 dent, I have the satisfaction to inform you, that Mr. Dollond has 

 been so kind as to favour us with a bust of his grandfather, John 

 Dollond. This memorial of one to whose ingenuity astronomy has 

 been so deeply indebted, will form a valuable addition to our gallery 

 of illustrious men. I am also able to congratulate the Society on 

 the acquisition made this day of a bust of the justly celebrated 

 James Watt, for which we have to give our most grateful thanks to 

 his son. When we contemplate the features represented with so 

 much spirit by a Chantrey, and copied so faithfully by a Hoffernan, 



vast additions of new corapounds produced by the application of artificial 

 agencies to existing organic products. To this progress M. Dumas has 

 greatly contributed by fixing attention on the removal of one element by 

 another, which occurs in these reactions, and in particular to the equiva- 

 lent substitution of chlorine for hydrogen, which has been successfully 

 executed in a variety of substances by M. Dumas himself, and by others 

 whom his discoveries and speculations have drawn into this fruitful field 

 of research. The preservation of certain fundamental properties in the 

 new compounds thus produced, he has referred to the existence of a pecu- 

 liar arrangement of t?ie constituent atoms in a compound, which arrange- 

 ment is supposed to be preserved on the removal of one atom, or success- 

 ive removal of several atoms, and their replacement by an equal number 

 of atoms of a different element, and is expressed by the " chemical type." 



In M. Dumas's first memoir on Chemical Types, his views are illustrated 

 by the discovery of diloro-acetic acid, a remarkable substance, and highly 

 interesting in its composition, being an acetic acid (vinegar), of which the 

 whole hydrogen has disappeared, but is replaced by an equivalent quantity 

 of chlorine. In this paper, also, he first forms ''marsh gas" by an arti- 

 ficial process, and shows its relation to the acetates. He also forms a series 

 of compounds by the action of chlorine upon marsh gas or " the gas of the 

 acetates." 



The second memoir of the series makes known the action of hydrated 

 potass upon the alcohols, and furnishes a new and simple method of pro- 

 curing the acid equivalent to a given alcohol. Thus acetic acid is alcohol, 

 in which two atoms of hydrogen are replaced by two atoms of oxygen, and 

 that acid is shown to be produced by the action of hydrate of potass upon 

 alcohol at a high temperature, with the evolution of hydrogen gas. To 

 estimate the value of these discoveries, it is necessar}^ to bear in mind the 

 importance lately acquired by the bodies of which common alcohol is the 

 type. To discover or characterize a body as an alcohol, is to enrich organic 

 chemistry with a series of products analogous to those which are presented 

 in mineral chemistry by the discovery of a new metal. M. Dumas then 

 applies this new method to other alcohols, and obtains by it formic acid 

 from wood- spirit, ethalic acid from the ethol of spermaceti, and valerianic 

 acid from the oil of potatoes. 



In the third memoir, M. Dumas, in conjunction with E. Pelegat, de- 

 scribes certain new compound ethers, containing carbonic acid, one of 

 which is remarkable for its analogy to sugar in its composition. 



In addition to this series, M. Dumas, in conjunction with M. Hasfone, 

 one of his numerous pupils, has given to the world the results of an elabo- 

 rate investigation of the atomic weight of carbon, in which, independently 

 of the importance of the analytical result obtained, certain defects of the 

 method of organic analysis universally practised are first pointed out, and 

 a degree of exactness and precision communicated to the process which it 



