348 Prof. Henslow on the Deluge, [Nov. 



Before replying to this question, I will ask what has been the 

 fate of the comet of 1770, whose periodic time was not greater 

 than five years and a half, and which could never wander so far 

 from the sun as to get beyond the orbit of Saturn ? Yet this has 

 not been since that time, and no solution of the cause of its 

 disappearance appears so probable as that offered by Dr. Brew- 

 ster, " that it now exists under the form of those enormous 

 atmospheres which accompany Ceres and Pallas." 



If it be loo much to suppose that the nucleus of such a comet, 

 though composed of aqueous particles, would fall to the earth, 

 we may, perhaps, conjecture that a portion of its nebulous train 

 becoming entangled m our atmosphere would be attracted to 

 the earth, and descend in the form of rain upon every portion of 

 its surface successively, as the earth turned upon its axis. This 

 conjecture as to the mode of supply is here mentioned, as I before 

 stated, with the view of promoting another inquiry upon a point 

 which seems to be pretty well established in geology, viz. that 

 the mean temperature of the earth's surface, at least in these 

 latitudes, has been very sensibly diminished ever since the 

 Deluge. If the mean temperature of the earth's surface 

 depend upon the distance of the centre of the earth from the 

 surface of the ocean, then the increase of waters brought by the 

 deluge would, by increasing the radius of the earth, produce 

 the phenomenon which has been observed. 



It may also be proposed as a subject of inquiry, what would 

 be the effect produced upon the atmosphere by increasing 

 the proportion of aqueous surface to that of the dry land. 

 Would the atmosphere become more highly charged with 

 aqueous vapour, and cause a greater quantity of rain to fall 

 annually ? We know that some of the planets possess an atmo- 

 sphere of extreme purity, and that others apparently have none. 

 Among the former number is the moon. Now it is remarkable 

 that the latest discoveries lead us to suppose that the moon pos- 

 sesses no seas, though there are large indentations on her surface 

 which would speedily become such, were she inundated by a 

 Deluge. 



How far such investigations as these may tend to confirm the 

 history of the rainbow having been first seen after the Deluge, 

 or, in other words, the non-existence of rain previous to 

 that event, I leave to the inquiry of meteorologists, requesting 

 them to bear in mind that the only account we have of the 

 method by which the earth was refreshed before the Deluge is, 

 that " there went up a mist from the earth and watered the 

 whole face of the ground ;" *' For the Lord God had not caused 

 it to rain upon the earth." 



I remain, Sir, your obedient servant, 



J. S. Henslow\ 



