16 Henry iJa-^aetf, Jun. — Prcjxn-ation of SpJierurttes. 



while even spherulites in glassy igneous rocks often show similar 

 colour-banding. This zoning out of the sulphanilic acid accounts 

 for the ragged edges of the rings, while the existence of a hollow 

 at the top of the mass where the spherical surface of the spherulites 

 can be seen also points to the liquid magma having thus been 

 soaked up. 



I have since several times repeated the experiment, and find that 

 the spherulitic structure is developed every time, provided that the 

 liquid is allowed to cool slowly, although even when cooled quickly 

 one or two may be formed. The size of the spherulites obtained 

 varies greatly ; on one occasion I prepared one which was two inches 

 in diameter, but, as is so often the case in nature, the moderate-sized 

 ones are generally the prettiest. Sometimes, after having left the 

 flask to cool, I found next day that the material had not all solidified,, 

 but that there was a floating crust with spherulites growing 

 downwards and also a solid layer at the bottom with spherulites 

 growing upwards, thus confirming the opinion as to independent 

 development from the two surfaces which I had formed from the- 

 examination of the first batch obtained. I should add, however, 

 that the spherulitic structure is not always developed on the free 

 surface of the mass, nor have I been able to prepare again the 

 spherulitic films (if I may so call them) on the sides of the flask. 

 The time taken for the mass to crystallize completely varies from 

 one to three days, depending, I imagine, on the amount of impurit}' 

 present. When the crj^stallization takes place very slowly it is very 

 beautiful to watch the small spherulites gradually growing in a dark, 

 almost black, magma, until finally it is completely transformed into 

 spherulites. In this intermediate state the specimen looks very 

 much like spherulitic obsidian. 



When the spherulites are formed very slowly the zones, which 

 are so noticeable in specimens which have formed more quickly, 

 are not nearly so frequent or well-marked. This perhaps is due to 

 the fact that, as the crystallization is so slow, diffusion is able to 

 prevent the magma round the centres of crystallization becoming 

 exhausted. 



I may add that the sulphuric acid present renders the mass very 

 deliquescent, so that in order to preserve it the flask containing it 

 should be sealed off in the blowpipe flame. 



After about two months' keeping the mass begins to recrystallize, 

 and, in course of time, the original structure is entirely obliterated 

 and replaced by an immense number of small spherulites about 

 1 mm. in diameter. This molecular change is curious, but the fact 

 that not even the external form of the original spherulites is pre- 

 served, is probably due to the presence of fluid, which, Avhen 

 recrystallization took place, was able to escape and collect at the 

 bottom of the flask. 



Mj' thanks are due to Mr. Coomara-Swamy for having very 

 kindly photographed the structure for me. This figure, however, 

 does not represent the best specimen, for the shape of the vessel 

 in which that had been formed was unfortunately unsuitable for- 

 photographing. 



