INSTRUCTION IN PHYSICS. 339 



iDoth of hydro-carbon and nitrogen compounds, confirm the conclusions drawn 

 from the identity of the paths of comets and meteoric-periodic shooting stars. 



5. Mr. H. A. Newton, in a remarkable paper read before the Sheffield 

 meeting of the British Association, 1879, showed the possibility (if not the prob- 

 abiUty) of the asteroids being extinct comets, captured and brought into the 

 solar system by the attraction of some one or other of the outer large planets, 

 and permanently confined in the space between Mars and Jupiter, which is the 

 only prison cell in the solar system large enough to hold permanently such dis- 

 orderly wanderers. 



In the same paper. Prof. Newton threw out the idea that some of the satel- 

 lites of the large planets might also be of cometary origin. From all these and 

 other considerations, it is therefore allowable to suppose that the earth and moon 

 when they separated from the solar nebula, did so as a swarm of solid meteoric 

 stones, each of them showing the temperature of interstellar space ; i. e. , some- 

 thing not much warmer than 460° F. below the freezing point of water. 



Mr. George H. Darwin has shown admirably how the earth-moon system 

 may have been developed from the time when the earth-moon formed one planet, 

 revolving on its axis in a few hours to the present time, when the earth and 

 moon (in consequence of tidal friction) have pushed each other asunder to a distance 

 of sixty times the radius of the earth. Dr. Haughton then entered into a lengthy 

 and most careful study of his paper, and il.ustrated it on the blackboard. He 

 concluded by saying that the remarkable expression found by Mr. Darwin is not 

 peculiar to his special hypothesis of a viscous earth, but can be deducted equally 

 well from the totally distinct hypothesis of an absolutely rigid earth retarded by 

 the tidal action of a liquid ocean. 



PHYSICS. 



INSTRUCTION IN PHYSICS. 



In this section Vice-President Mendenhall read a paper on "Instruction in 

 Physics," of which the following is a synopsis : 



Out of respect for sciences as old as science itself, we have freely accorded 

 the first rank, as far as a designating letter may be able to imply it, to our vet- 

 eran co-laborers, the mathematicians and astronomers. This separation of physics 

 from astronomy and mathematics, as well as from chemistry, mechanics, etc., 

 must be considered as temporarily convenient for the purpose of specializing the 

 powers of the Association. We were mistaken in supposing that science had 

 only advanced through contributions — the result of original research m our lab- 

 oratories and libraries; even were so narrow a view taken, the existence of such 



