

Henry's Chemistry. 347 



with considerable rapidity. When thrown into water, it decom- 

 poses that liquid, with considerable rapidity." 



"By exposure to the air for some time, zinc acquires a greyish 

 colour on the surface, which is owing to a partial oxidizement. 

 Zinc filings very slowly decompose water, hydrogen gas is evolved, 

 and oxygen combines with the metal *." 



" A temperature of, from 120° to 140° Fahr., renders water 

 decomposable by iron, especially when the metal bears a con- 

 siderable proportion to the water f." 



We apprehend that the arrangement of the metals, best adapted 

 for students, would be to begin with the alkalifiable, next to 

 proceed to the geofiable, whereby a knowledge of the alkaline 

 and earthy re-agents, so useful in metallic research, would be ac- 

 quired at the outset. So far our plan agrees with Dr. Henry's. 

 The ordinary metals might then be examined as nearly as possi- 

 ble in the order of their affinities for oxygen, terminating the list 

 with platinum, and its companion metals. The old distinctions of 

 metals, and semi-metals, perfect and imperfect, base and noble, 

 should be forever banished from chemical discourse. They are 

 all the perfect and noble productions of nature, and the multipli- 

 cation of their species is one of the chief achievements of modern 

 science. 



We have looked over our author's 10th and 11th chapters on 

 vegetable substances, and their decomposition, as well as the 

 12th, on animal substances, and the 13th on animal products. 

 Wc think that the facts are judiciously abridged, and fairly stated. 

 The 14th chapter on chemical analysis is divided into 3 sections ; 

 of which the first treats of gaseous analysis, the second of that 

 of mineral waters, and the third of that of minerals. In these 

 details, he has followed Thenard and other writers on analysis 

 with fidelity. We could have wished him to have been a little 

 less sparing of references to the works from which he has bor- 

 rowed. "Nothing," says poor Richard, " gives an author so 

 great pleasure as to fine* his works respectfully quoted by others." 

 In the preceding article we have diligently exposed what to us 

 appear the prominent errors and principal failures in Dr. Henry's 

 Book, in the hope that our remarks may influence the merits of his 

 tenth edition, and in the belief that lie will not be offended with the 

 freedom of our strictures. In conclusion, we must add that there 

 is very much more to praise than to censure, in this work ; in mat- 

 ters of detail it will furnish a valuable guide to the chemical stu- 

 dent, and will uphold the reputation of its author, as a candid and 

 careful compiler, who speaks of his own inquiries without egotism, 

 and who discusses controverted, abstruse, and uncertain points, 

 with that becoming diffidence and candour which shows him (with 

 the Daltonian exceptions above-named) " nullius addictus in 

 verba niagistri." 

 • Aft- II. Davys EkiiujnU, 374. 1 Henry's Elements, 9th Edit. II. 17. 



