1826.] Proceedings of Philosophical Societies, 289 



references to other authors, for surely many of these birds must 

 have been described by Azara, and named by Vieillot; and that 

 the generic characters are not more distinctly defined. How- 

 ever, with these faults, which maybe corrected as the work 

 continues, we strongly recommend it to the public libraries of 

 this kingdom. *'• ^- ^' 



Article XII. 



Proceedings of Philosophical Societies. 



ROYAL SOCIETY. 



Feb. 23 (contimied).— Edmund Davy, Esq. lately elected, 

 being unable to attend for admission, requested that his name 

 might be inserted in the printed lists of the Society, which was 

 granted accordingly. The following is an abstract of Mr. Dal- 

 ton's paper on the Constitution of the Atmosphere, read at this 

 meeting. 



After some preliminary remarks, the author observes, that 

 whatever may be thought of Newton's hypothesis as to elastic 

 fluids, as far as the mechanical effects of such fluids are objects 

 of inquiry, we may safely adopt it ; namely, that each fluid is 

 constituted of particles repelling one another by forces inversely as 

 their central distances, at least within ordinary limits of conden- 

 sation and rarefaction. 



After adverting to the fact that mixtures of various elastic 

 fluids, such as is the atmosphere, composed of atoms of different 

 volumes and elasticities, do notwithstanding observe the same 

 laws of condensation and rarefaction as simple elastic fluids, and 

 to the difficulties which this fact throws in the way of the New- 

 tonian hypothesis, Mr. D. puts a case which he thinks has not 

 before been considered, and which may assist us materially ia 

 forming a correct notion of such mixed atmospheres. 



Two equal cylindrical pipes are conceived to be placed perpen- 

 dicular to the horizon, in contact, and of indefinite length, close 

 at the bottom, and open at the top. These are supposed to be 

 filled with two gases of different kinds, the one with carbonic 

 acid, and the other with hydrogen, in order to show the contrast 

 more strikingly. The columns of gases are assumed each to be 

 of the weight of 30 inches of mercury, and consequently \yill 

 represent vertical columns of atmospheres of the respective 

 gases equal in weight to like columns of the earth's atmosphere. 

 Mr. D. calculates from known principles that the column of car- 

 bonic acid gas will terminate at 30 or 40 miles of elevation, or at 

 least will become of such tenuity as that it may be disregarded. 

 In like manner that of hydrogen will be found to become insig- 

 nificant above 1200 miles of altitude. The author then supposes 



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