4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 92 



like structure in the clouds, still more delicate, and whose faint intri- 

 cate outlines tease the eye, which can neither definitely follow them, 

 nor analyze the source of its impression of their existence. 



" These appearances have been mentioned, lest they should be con- 

 founded in any way with the far minuter structure now to be 

 described. 



" Under high powers used in favorable moments, the surface of any 

 one of the fleecy patches is resolved into a congeries of small, intensely 

 bright bodies, irregularly distributed, which seem to be suspended in a 

 comparatively dark medium, and whose definiteness of size and out- 

 line, although not absolute, is yet striking by contrast with the vague- 

 ness of the cloud-forms seen before, and which we now perceive to be 

 due to their aggregation. The ' dots ' seen before are considerable 

 openings caused by the absence of the white nodules at certain points, 

 and the consequent exposure of the gray medium which forms the 

 general background. These openings have been called pores ; their 

 variety of size makes any measurements nearly valueless, though we 

 may estimate in a very rough way the diameter of the more conspicu- 

 ous at from 2" to 4". The bright nodules are themselves not uni- 

 formly bright (some being notably more brilliant than their fellows 

 and even unequally bright in portions, of the same nodule), neither 

 are they uniform in shape. They have just been spoken of as rela- 

 tively definite in outline, but this outHne is commonly found to be 

 irregular on minute study, while it yet affects, as a whole, an elongated 

 or oval contour. Mr. Stone has called them rice-grains, a term only 

 descriptive of their appearance with an aperture of three to four 

 inches, but which I will use provisionally. It depicts their whiteness, 

 their relative individuality, and their approximate form, but not their 

 irregular outline, nor a certain tendency to foliate structure which is 

 characteristic of them, and which has not been sufficiently remarked 

 upon. This irregularity and diversity of outline have been already 

 observed by Mr. Huggins. Estimates of the mean size of these bodies 

 vary very widely. Probably Mr. Huggins has taken a judicious mean 

 in averaging their longer diameter at i".5, and their shorter at i", 

 while remarking that they are occasionally between 2" and 3" and 

 sometimes less than i" in length 



" In moments of rarest definition I have resolved these ' rice- 

 grains ' into minuter components, sensibly round, which are seen 

 singly as points of light, and whose aggregation produces the ' rice- 

 grain ' structure. These minutest bodies, which I will call granules* 



^As this word is already in use, with another meaning, attention should be 

 given to the restricted and definite significance which is here assigned to it. 



