30(> Analyses of Books, [Oct, 



aud by the subsequent proof that more azote exists in the. 

 residue than ought to do, on the supposition the hygrogen wa^ 

 quite pure. 



Such persons as are not familiar with this kind of experi- 

 ment, and wish to repeat any of them, will do well to remem- 

 ber that whenever oxygen and hydrogen are mixed in nearly the 

 saturating prqportiom, the mixture should stand some time 

 (five minutes,) in order to allow of the perfect diffusion of the 

 gases, before the spark is given. 



I remain, yours truly, Jqhn Dalton. 



Article XIV. 

 Analyses of Books. 



Journal of the Academy of Natural Sciences of Philadelphia, 

 Vol. iv. Part 2. 



This volume contains 22 papers on various subjects of 

 Natural History, and is illustrated with eight plates, two of 

 •which (tab. 20 and 21) engraved by Mr. A. Lawson, of Phila- 

 delphia, from drawings by Lesereur and Mr. A. Rider, are the 

 most beautifully executed plates of natural history subject which 

 we have seen from any American art, not even excepting the cele- 

 brated plates of the Wappity and Marmot, by the same artist. 

 These plates are lent to the society by Mr. Ord. 



There are three papers relative to Mammalia. 



1. An Account of a New Species of the Genus Arvicola. By 

 George Ord, p. 305. 



Arvicola raparius. Snout thick, blunt; eyes small; ears 

 middle-sized ; tail less than half the length of the body. This 

 species is fond of the seeds of wild rice and oats, zizania 

 aquatica. 



2. A new Genus of Mammaha proposed, and a Description of 

 the Species upon which it is founded. By T. Say and G. Ord, 

 p. 345. 



Genus Nectoma; character, teeth -, cutting - grindery r-^, 



with deep radicles ; tail hairy ; toes 4-5, 



This genus ig allied to Arvicola, and, indeed, Dr. Harlan ha? 

 placed the species in that genus. 



N.Jloridana. ^nout elongated; eye^ and e?ir^ very large; 

 tail longer than the body. t. 21 ; length frpipi snout to vent 

 7^ inches; tail 6^ inches. 



; This animal was first described by Mr. Ord in the Bulletin of 

 ihe Philamaton Society as Mus Floridanus. 



