C'OllRESPONDLNCi: 



215 



Causes of Cosmical Changes of Temperature on our Planet. 



It is admitted that the possible changes in the present meteorological 

 conditions of our planet could not account for the great fluctuations of tem- 

 perature recorded in the geological history of the glacial periods. Mr. 

 IS. J. Mackie, in the last number of the ' Geologist,' attributes these 

 changes of temperature to changes of size of the sun's disk, to maximum 

 and minimum periods of solar heat, etc. etc. It is clear these explanations, 

 although possible, are purely arbitrary, mere speculations, unsupported by 

 any cosmical or physical facts. Now, it is known that our solar system is 

 travelling in space towards the constellation Hercules at the rate of 57^ 

 miles a second ; yet so great are star-distances, that thousands of years 

 elapse before our visible position in the heavens be changed to the naked 

 eye. From the observations of Glaisher in his balloon ascents, it appears 

 that the decrease in temperature is not in direct proportion to tbe distance 

 from the earth ; but, on the contrary, that a hundred feet elevation at the 

 earth's surface produces as great refrigeration as a thousand feet at a 

 greater elevation. It necessarily follows that we must arrive at cosmical 

 temperature beyond the influence of atmospheric changes ; but is this 

 cosmic temperature uniform through the portions of space destined to be 

 traversed by our solar system ? If there be portions of space of different 

 cosmical temperatures through which our planet has passed, this would 

 account for the great cold of the glacial periods in a way supported by one 

 strong fact, which is, that our position in the heavens is changing at the 

 rate of 57^ miles a second, and for this change of position not to affect the 

 heat of our earth, we must suppose the cosmical temperature of space so 

 traversed by our earth to be uniform, which would be a most arbitrary 

 supposition. It is quite possible, nay even probable, that not only our 

 ow n solar system, but all visible creation, the infinite and countless stars, — 

 so remote, that their light has taken millions of years to come to our eye, — 

 are all revolving through space around some almost infinitely far-off cent re, 

 which if luminous, its light is so attenuated by distance as to be invisible 

 to us, and that the period of such a revolution may be long, beyond all 

 calculation, during which immense portions of space must be traversed, 

 most likely of unequal cosmic temperature, quite sufficient to account for 

 the glacial periods in the geological history of our earth. There is nothing 

 fanciful in this view, or beyond the range of probability. The vas1 magni- 

 tude of such a system is no objection to its existence, for, in comparison 

 with infinity, all assignable distance or magnitude shrinks into a mere 

 point. The immense period necessary for such a revolution would afford 

 ample time for all the glacial formations recorded by geological observa- 

 tion, by admitting only the natural supposition that the temperature of 

 infinite space is not uniform. Yours, etc., David Leslie, M.D. 



Carrickmacross, Ireland, Mai/ 21, 1863. 



[It is not the intention of the Editor to reply to comments on his articles in all ease- 

 separately, but in one or two respects Dr. Leslie's letter requires notice. Mr. Mackie 

 distinctly put forward t lie views in his paper speculations } hut Dr. Leslie is wrong 

 in saying they are all unsupported by physical or cosmical facts. Neither is it admitted 

 that possible changes of meteorological conditions couhl not lane produced the cold of 

 the glacial era. It may have been dogmatically asserted so. Wc should be glad to 

 learn what temperature Dr. Leslie thinks existed then, and what were the fluctuations it 

 was subjected to. We should also be glad to know on what grounds the idea of hot 

 and cold regions in space can be maintained ; ami why the cosmical temperature of space 

 should not be the real zero of temperature, or a condition of absence of all heat. We 

 should like to know what is the presumed tempi raturc of the cold cosmical space through 

 which our globe is so hypothctically supposed to have passed in the glacial nge. — Ed. 



Gaot.] 



