820 Transactioi\s of the Am eric ax Ixstitvte. 



tlie ray continues, often for Imndreds of miles l)ejond a basin which 

 it lias passed over, it is evident that the fluid agent from which it 

 was deposited must have filled the basin up before it could by any 

 possibility pass over it, all of which implies that the rays are but 

 the sedimentary traces of the agent which produced them ; had it 

 been lava, the basin would have remained full. 



"When the ray is continuing its course, passes out of the basin 

 the drift from the fractures through which it has emerged is inva- 

 riably to be found outside of the wall, and resembles exactly tlie 

 forms of the drifts of clay and sand which may be found in the bed 

 of any stream on the lower side of islands, boulders, or other obstruc- 

 tions which may have intercepted the flow of the water. A fine 

 example of this formation is to be found in the first quarter moon 

 made by Mr. Rutherford. In this it will be seen that some of the 

 rays from Tyclio have almost depleted the ramparts of several rings, 

 including those of Stofler, Fernelius and Nonius, Here the larger 

 masses of the rims which survived the action of the depleting force, 

 have, behind them on tlie side, away from Tyclio, the peculiar drift 

 formation referred to. "Wherever a small. cone of the lesser forma- 

 tions has survived the action of the force which may have directed 

 the ray against it, the course of the ray itself will be changed, or else 

 leave the appearance of a long line of drift behind the obstructions 

 after sweeping round its base. 



Speaking in a general wa}', the ring formations have an altitude 

 on the outside of something less than a mile, and on the inside they 

 are nearl}- three times this height from the apex of the rim to the 

 floor of the basin. Then, if we suppose the surface of the ray forma- 

 tion in the immediate neighborhood of Tycho to be even a mile above 

 the general level, though in fact it is never so high as the ring of the 

 basin, but even if it were, it would not then have a descending grade 

 of over seven feet to the mile, and assuming this to be a fair repre- 

 sentation of the ray systems of the moon, you will at once perceive 

 that such a fact alone removes the M^hole of the lunar formation out 

 of the catalogue of volcanoes. Such gentle grades as this could only 

 be formed by matter in a fluid state, as mobile as water ; nor could 

 water flow over such slight inclinations if it were very deeply laden 

 with sedimentary matter. 



Volcanic Origin of the Lunak Formations Doubtful. 

 The volcanic cones upon the surface of the earth are very few and 

 far between, while upon the moon the basins called volcanoes may be 



