340 Analysis of Scientific Books. 



the slightest degree, to disparage Mr. Dalton's great merit in 

 establishing, so ably as he has done, the important system of re- 

 ciprocal and multiple combination. We wish merely to see it 

 stripped of all such trappings as disguise and disfigure it. Among 

 these, the following two positions of Mr. Dalton, expounded by 

 Dr. Henry, may be reckoned. 1 . That an increase of the density 

 of a gas, indicates an increased number of simple atoms, associated 

 in the compound atom. 2. " Moreover, it is universally observed 

 that of chemical compounds, the most simple are the most difficult 

 to be decomposed ; and this being the case with carbonic oxide, 

 we may naturally suppose it to be more simple than carbonic acid*." 

 Dr. Henry clenches the first position as follows : — " It would he 

 absurd to suppose carbonic acid, which is the heavier body, to be 

 only once compounded, and carbonic oxide, which is the lighter, 

 to be twice compounded t" 



The first position goes to prove that nitrous oxide, a denser gas 

 than nitrous gas, has an increased number of simple atoms, or is 

 more than once compounded. Such is Mr. Dalton's own decision 

 in this very case. The nitrous gas being the lighter, is the simpler 

 body, or is only once compounded. 



By the second position, however, nitrous gas is not the simpler 

 body, but is more than once compounded, for it is decomposable 

 by a great many substances which have no effect on nitrous oxide; 

 such as moistened iron or zinc filings, muriate of tin, alkaline sul- 

 phites, and aqueous solutions of sulphurets. Thus nitrous oxide is 

 " the most simple, as it is the most difficult to be decomposed." 

 But by the first Daltonian article, it is the most compounded, or 

 least simple ; which is absurd. We shall leave the framer and 

 expositor of these fancied axioms, to assist each other in getting 

 off the horns of the dilemma at their leisure. 



We felt, we must confess, a little alarmed when we first heard 

 Doctor Henry talk so boldly of the " well-ascertained exceptions" 

 to the hypothesis of volumes, which were to render " the theory of 

 volumes scarcely tenable." But on hunting after his exceptions 

 with some curiosity, we could not find one of them forthcoming in 

 his two volumes. Truly, if the theory of volumes, as developed 

 by Gay-Lussac, shall be found scarcely tenable, we know of nothing 

 in chemical science to which we can venture to attach the anchor 

 of our belief, for nothing is better demonstrated than that theory. 



In the above instances our author has merely mistaken the par- 

 tial enactments o f his ingenious friend, for the laws of nature. But 

 we shall see him presently enlist his ideas in foreign service, and 

 advance doctrines incompatible with the principles of his English 

 master, while he fondly imagines himself the true defender of the 

 faith. 



In section 5th, speaking of Berthollet's doctrines of affinity, he 

 very properly quotes Professor Pfaff's experiments, to prove that 

 * Henry's Mem. 1, 50. f lbidm, loco tilato. 



