Dr. Thomson — and his Answer. 345; 



blunder; yet, on that ludicrous bottom, he rested his refutation- 

 of experiments on the constitution of carburetted hydrogen,, 

 conducted with very considerable care. " The Reviewer," 

 says he, "has misstated my reasoning in the Annals ; but it 

 is not worth while to put him right." This statement is alto- 

 gether false, as the following quotation will prove. Here is the 

 Doctor's equation from the Annals of Philosophy. 



B + A 

 In the present case, ^4 =: 1 . a = 0.9722 

 B =z 0.66 b = 0.0694 

 Consequently . = 0-66 X 0.0694 + 0.9722 ^ ^^ gg^^g ,. 

 1.66 



Now we affirm that the youngest school-boy will laugh at such 

 a shallow algebraist : for taking his own formula and numbers ; 

 X =. 0.611 and not 0.86178. We shall be curious to see what 

 subterfuge will next be adopted, in order to escape from this 

 dilemma. 



We shall now quote a passage from our Review, to shew the 

 Doctor's mode of reply. " The following sentence shews 

 the Doctor's incompetency as an experimentalist. ' Unless 

 the flask be very completely exhausted indeed of common 

 air, combustion takes place, when the phosphuretted hydrogen 

 is let into it.' ' This confession betrays poverty of invention, 

 and ignorance of the methods previously practised in such 

 cases. If the Doctor will consult Sir H. Davy's Bakerian Lec- 

 ture on the Alkaline Metals, he will find this philosopher, filling 

 his flask with hydrogen, and then exhausting that gas, in 

 order to get rid entirely of the atmospheric oxygen." " I 

 affirm," says he now, " that my method is susceptible of 

 greater accuracy than that which the Reviewer insinuates, that 

 1 did not know *." His method, which is the old one, of com- 

 paring the weight of a flask filled first with air, and then with any 

 gas, certainly does not remove the fallacy of which he himself 

 complained in the above quotation, arising from the partial 

 combustion of the phosphuretted hydrogen, by the residuary air; 

 and, indeed, since his air-pump always leaves a notable re- 

 siduum of common air in his flask, " his method" is totally 

 inapplicable to phosphuretted hydrogen. We would advise 

 him to fill his flask after the first exhaustion, with azote, and 

 not till after a second, or, perhaps, a third operation, to 

 admit the combustible gas. 



But the boasting tone in which he talks of his superior skill in 

 taking the specific gravity of gases, is finely contrasted with his. 

 total ignorance of the subject. Thus Dr. Thomson speaks of 

 himself as a person " who has determined the specific gravity 



* Annwer, p. 968. 



