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168 PROF. O. REYNOLDS ON THE FORMATION OF 



nuous is truly conical, or rather pyramidal ; but this sur- 

 face is broken, as it were, by steps ; and a very marked fact 

 is that all the continuous surfaces have the same vertex ; 

 and hence the different conical surfaces to which they 

 belong have not the same vertical angle, the surface being 

 exactly such as would be acquired by the fragments of a 

 sphere so constituted that the fracture tended to follow 

 radial lines. 



Owing to the radiation of the surfaces from a common 

 vertex and the steps which occur between the vertex and 

 the base, the angle of the conical surface of the stone is 

 greater near the vertex than near the base. Thus the 

 smaller stones appear less elongated than those which are 

 larger. 



The fact that in the sketches of actual stones, which I 

 gave in my last paper, I showed the steps as less pronounced 

 and the angles as larger than they are in the artificial stones, 

 is probably owing in some measure to my haviug formed 

 my ideas from the observation of favourable specimens 

 chosen from amongst those which fell. The larger angles 

 were probably also, in part, owing to the smaller size of 

 the actual hailstones, which were not much more than one 

 fourth of an inch across. But I think that it is important 

 to notice that the somewhat imperfect way in which the 

 outside layers in the surface of the artificial stones are con- 

 tinued may be owing to the narrowness of the jet of air, 

 which, on striking the stone, tends to diverge laterally 

 rather than to flow upwards past the sides of the stone, as 

 it would do if the jet were broader, or as the air must do 

 when the stone is falling through it. 



The rate at whichstones can be formed depends on the 

 amount of Avater which can be introduced into the spray, 

 the larger stones taking from one to two minutes. At 

 first sight this may seem to be somewhat slow ; but the fol- 



