A7A' WILLIAM .s/A.l/AW.V, RK.S. 433 



similar to meteoric stones. Adopting this view, and assuming 

 thin the stones have absorbed in stellar space gases to the amount 

 nl' six tiiiR's their volume, taken at atmospheric pressure, what, it 

 may be asked, will be the effect of such a mass of stone advancing 

 towards the sun at a velocity reaching in perihelion the prodigious 

 rate of 3GU miles per second (as observed in the comet of 1845), 

 being twenty-three times our orbital rate of motion. It appears 

 nt that the entry of such a divided mass into a comparatively 

 dense atmosphere must be accompanied by a rise of temperature 

 by frictional resistance, aided by attractive condensation. At a 

 in point the increase of temperature must cause ignition, and 

 the heat thus produced must drive out the occluded gases, which 

 in an atmosphere 3000 times less dense than that of our earth 

 would produce 6 x 3000 =18,000 times the volume of the stones 

 themselves. These gases would issue forth in all directions, but 

 would remain unobserved except in that of motion, in which they 

 would meet the interplanetary atmosphere with the compound 

 velocity, and form a zone of intense combustion, such as Dr. 

 lluggins has lately observed to surround the one side of the 

 nucleus, evidently the side of forward motion. The nucleus would 

 thus emit original light, whereas the tail may be supposed to con- 

 sist of stellar dust rendered luminous by reflex action produced by 

 the light of the sun and comet combined as fore-shadowed already 

 by Tyndall, Tate, and others, starting each from different assump- 

 tions. 



These are in brief the outlines of my reflections regarding this 

 most fascinating question, which I venture to put before the 

 Royal Society. Although I cannot pretend to an intimate ac- 

 quaintance with the more intricate phenomena of solar physics, I 

 have long had a conviction, derived principally from familiarity 

 with some of the terrestrial effects of heat, that the prodigious and 

 seemingly wanton dissipation of solar heat is unnecessary to satisfy 

 accepted principles regarding the conservation of energy, but that 

 it may be arrested and returned over and over again to the sun, in 

 a manner somewhat analogous to the action of the heat recuperator 

 in the regenerative gas furnace. The fundamental conditions 

 are : 



1. That aqueous vapour and carbon compounds are present in 

 stellar or interplanetary space. 



VOL. ii. p r 



