rr=; 



290 Monograph of the Genus Sdurus. 



ent ; and as the volumes are inversely as the specific gravities 

 they are found by dividing the weights by the sp. gr. of each. 



We give as an example the mixture of oxygen and azote in 

 atmospheric air. 



l.llil- 1.1111 x.9722._ 309 

 — 1 1111— 9722 1389 = P^^^portional weight of 



oxygen. 



_ l.llllx.9722- .9722 1080 



^ rilll-.9722 ~1389~ ^^' ^^- ^^ 



Azote. 



Now since 100 cubic inches of air weigh 30.5 grains, it will 

 be found that the weight per cent, of oxygen in atmospheric air is 

 22.23, and of azote 77.77, divide these by the sp. gr. of each, 

 and it will be found that the volume per cent, of azote is 79.8 

 that of oxygen 20.2 nearly, which corresponds exactly with the 

 result of the most rigid and careful experiments. 



I need scarcely remark that this formula applies only in cases 

 where the specific gravities are determined by the same standard 

 of comparison, although in every case they may be reduced to 

 the same by an easy mathematical calculation. 



Liberty Co., Geo., Aug. 15th, 1839. 



Art. XVII. — Abstract of a Monograph of the Genus iSciurus, 

 with descriptions of several nexo species and varieties ; by 

 J. Bachman, D. D.J President of the Lit. and Phil. Soc. of 

 Charleston, S. C* 



Many of the species of this very widely difiused genus are, 

 through the influence of cHmate and other alterative causes, 

 subject to remarkable variations, which have proved a fruit- 

 ful source of error in characterizing the specific forms of such 

 as inhabit the Old World. 



From the vastness of the territory over which they are dis- 

 persed, still greater difficulties have presented themselves in de- 

 scribing and separating the species of Sciuri peculiar to our own 

 continent. Their anatomy and habits through the whole genus, 

 present striking similarities, while on the other hand differences 

 nearly as remarkable both in size, color and habit, are observable 



* Abridged from Mag. of Nat. Hist, for March, 163!), ct seq. 



