202 PROCEEDINGS OF THE ACADEMY OF 



Prof. Robert E. Rogers made some remarks on the fallacies that arose from 

 '.he ordinary use of language, when applied to the description of phenomena in 

 a scientific manner. He adverted to the subject of combustion to illustrate his 

 views, and showed that our ordinary explanation of what is called by this 

 r.ame, where one of the substances is styled a combustible, and the other a sup- 

 porter of combustion, as for example, in the burning of an ordinary gas light, 

 was fallacious, because we only looked at it from one point of view. The gas 

 to be burned was comparatively small in quantity, and the oxygen surround- 

 ing it was in large amount ; hence the gas alone appeared to burn the oxy- 

 gen of the air to support it. When, however, we surround the oxygen with a 

 large quantity of gas, or, so to speak, with an atmosphere of gas, thus reversing 

 entirely the conditions, then the oxygen burns, and the gas becomes a support- 

 er of combustion. We have then no right to call the gas a combustible any 

 more than the oxygen ; or the oxygen a supporter of combustion, any more 

 than the gas. The action between the two bodies is mutual, and the various 

 phenomena witnessed are the result of that mutual action. The Professor 

 then exhibited a beautiful experiment, in which, after first burning the com- 

 mon illuminating gas in the ordinary way, he reversed the conditions, and 

 burned a jet of common air in an atmosphere of gas. 



June 19 th. 

 Mr. Lea, President, in the Chair. 



Twenty-one members present. 



The following papers were presented for publication : 



" On the identity of Ammonites Texanus, Roemer, and A. vesper- 

 tinus Morton," by Wm. M. Gabb. 



" Descriptions of three new species of Gorgonidse in the Collection 

 of the Academy of Natural Sciences of Philadelphia," by George W. 

 Horn. 



And were referred to Committees. 



June 26th. 

 Mr. Lea, President, in the Chair. 

 Thirty-one members present. 



The following papers were, on the report of the Committees to which 

 they had been referred, ordered to be published in the Proceedings : 



(to the Identity of Ammonites Texanus, Koemer, and A. vespertinus, Morton. 



BY W. M. GABB. 



In 1834, Dr. Morton described, an ammonite from Arkansas, in his synopsis, 

 under the name of A. vespertinus. The type, consisting of two fragments 

 of an individual, apparently about fifteen inches in diameter, is in the collec- 

 tion of the Academy. 



As long ago as September of last year, I was struck with the resemblance 

 of these specimens to the species described by Roemer, in " Kreidebildungen 

 von Texas," 1852, under the name of A. Texanus. The originals of 

 Dr. Morton's species were so weathered that I was unable to make out the 

 septum. 



More recently, however, through the kindness of Dr. Moore, I have been 

 enabled to procure an undoubted specimen of A. Texanus, consisting of 

 nearly the whole outer whorl of an individual, about a foot in diameter. On 

 comparing this with Morton's specimens, I became convinced of their identity. 

 The names will therefore have to be A. vespertinus, Morton; A. 

 Texanus, Roemer, being a synonyme. 



[Jane, 



