Dr, Lhomson’s First Principles of Chemistry. 168 
cesses, frequently to the eight or tenth time—the consum- 
mate skill discovered in devising and executing the experi- 
ments, and the surprising coincidence of the results of analy- 
sis, with the deductions of theory, excite ourastonishment, and 
prove, beyond a question, that chemistry, if not founded inin- 
tuitive, is built on demonstrative truth. Dr. Thomson, after 
performing so much, might have well adopted a motto prefer- 
ring higher claims than that which he has chosen: i.¢€. 
** Ut potero, explicabo; non tamen ut Pythius Apollo, certa 
ut sint et fixa, que dixero: sed ut homunculus, probabilia 
conjectura sequens.’” ‘Tusc. Quast. Lib. I. c. 9. 
Dr. Thomson has dedicated his work to those eminent 
philosophers, Mr. Dalton, Prof. Gay Lussac, Sir Humphrey 
Davy, Prof. Berzelius, Dr. Wollaston, and Dr. Prout, who - 
have laboured so successfully in the same field, and notwith- 
standing some differences of opinion among these gentlemen, 
they will doubtless hail the work of Dr. Thomson as a vast 
acquisition to the Atomic theory. Dr. Thomson does not 
always agree with the views of Prof. Berzelius, but he does 
justice to the exalted merit of the Swedish philosopher, to 
whom the science of chemistry is under such great obliga- 
tions, 
The great fundamental truth is now established beyond 
all controversy, that every body enters into chemical combi- 
nations always with the same weight, or with a weight bear- 
ing an accurate arithmetical ratio, to the smallest weight of 
the given body which is capable of entering into combination : 
hence, some body being agreed upon as a unit, the weights 
of all others can also be expressed by numbers, which will 
always represent one proportion, or two, ormore, of the com- 
bining body. Unfortunately the gentlemen who have writ- 
ten in support of the atomic theory have been divided be- 
tween oxygen and hydrogen for the unit. This occasions 
considerable inconvenience to learners, because different 
numbers are of course used to denote the weight of the same 
he but it affords no ground toassail the theory as untena- 
le. 
We annex some extracts from a letter received from Dr. 
Thomson, by which it will appear that he is still prosecuting 
this important inquiry, and that we may hope to hear from 
_him again on the subject. 
