140 Anali/sis of Scientific Books. 



style. He distributes them into supporters of combustion, 

 incombustibles, and combustibles. " The term supporter of 

 combustion, I apply to those substances, which must be pre- 

 sent before combustible bodies will burn." That a chemical 

 author, at the present day, should assume the narrow notions 

 of Becher and Stahl, as the groundwork of his system, is truly 

 wonderful. Dr. Thomson contemplates chemistry solely as a 

 process of combustion, instead of considering combustion as an 

 accident of chemical combination; what is merely an adven- 

 titious and occasional accompaniment of its phenomena he 

 mistakes for the soul of the science. 



Oxygen, chlorine, iodine, and fluorine, are the subjects 

 he chooses to begin with ; and seeing that he furnished no 

 preliminary explanations of the principles of chemical action 

 and research, they are quite sufficient to perplex and confound 

 the student at his outset. In treating of oxygen, he gives a 

 wooden cut of an iron bottle, and two of a pneumatic cistern, 

 which he describes twice over, in two consecutive pages, in 

 nearly the same words ; these water-troughs differ only in the 

 second having four clumsy feet, while the first has none. The 

 whole article oxygen, is re-printed verbatim. He never mentions 

 chlorate of potash, nor red oxide of mercury, as convenient sub- 

 stances from which it may be obtained pure; though the former 

 is always used with that view for accurate researches, and the 

 latter affords it elegantly to the student, by means of a bent glass 

 tube, sealed at one end. He gives no instructions for ascer- 

 taining, whether the gas which comes over from the bleacher's 

 manganese, be pure enough for collecting. *' Oxygen gas," 

 says he, " is not sensibly absorbed by water, though jarfuls 

 of it be left in contact with that liquid." Why does he not 

 state, that if " jarfuls of it be left in contact with that liquid" 

 in the pneumatic trough for a few days, it is so altered as to 

 be unfit for experimental purposes? He omits, also, to direct 

 " the tyro just beginning the study," to withdraw the iron 

 bottle from the fire, or to remove its beak from the water, as 

 soon as gas ceases to issue, and before the heat subsides, 

 otherwise the water may be forced into the bottle, so as to 

 cause explosion. 



" The weight of an atom of oxygen in the subsequent part of 

 this work will be denoted by, 1st. a volume of oxygen is equi- 

 valent to two atoms, provided, we suppose, as / have done, 

 that water is a compound of one atom of oxygen and one atom 

 of hydrogen." This hypothetical sentence is thrown at once on 

 the student without preface or commentary. 



The second section treats of chlorine, and is also a verbatim 

 re-print. " As soon as the phial is full, it is to be withdrawn, 

 and its mouth carefully stopped with a glass-stopper, accurately 

 ground so as to fit, and tvkick must be previously provided ." It 



