COMPOSITION AND STRUCTURE OF METEORITES 53 



of chondrules. It is to be noted, however, that they break away from 

 the matrix leaving a smooth concavity simulating the chondrules in 

 the tuffaceous meteorites — spherulitic chondrites. 



Among a series of specimens brought from the Hawaiian Islands 

 in 1920 by Dr. H. S. Washington were some loose aggregates of 

 fine volcanic ash labelled "fossil rain" from the Kilauea eruption 

 of 1790. These are often pisolitic, strongly suggestive of the chon- 

 dritic structure so pronounced in meteorites of the Bjurbole type. 

 The entire mass, however, pisolites and all, quicldy falls to pieces 

 when wet, and shows itself to consist of finely comminuted glass and 

 the silicate minerals characteristic of the lavas of this flow. The 

 chondroidal forms are entirely fragmental and the particles show no 

 order in their arrangement. Apparently they have originated in 

 place and are due merely to a haphazard aggregating of the finer 

 particles in the ash through the influence of water falling in the 

 form of fine drops such as would result through the condensation 

 of steam. Such forms are readily imitated in this same dry ash by 

 gently dropping into it small, isolated drops of water, and hence 

 the expression "fossil rain" which, though on many accounts objec- 

 tionable, is expressive. The pisolites described above are apparently 

 of the same nature as those occurring in ash from the Krakatoa 

 craters and figured by Friedlander.^^ Like forms are to be found in 

 ash from Pompeii. In these last the spherules are somewhat harder 

 and effervesce for a time when treated with a dilute acid, after which 

 they are readily reduced to a mud by crushing between the fingers. 

 Prof. J. A. Udden has described ^* the formation of small pellicles 

 of a somewhat similar nature occurring in a volcanic ash in McPherson 

 Countj^, Kansas. These he ascribes to wave action. However, their 

 resemblance to the meteoric chondrules is purely superficial. 



A beautiful illustration of apparent chondritic structure is furnished 

 by the basaltic tuff from the "Anterior Lava Sheet" of Connecticut 

 described by W. G. Foye.^^ The stone is fine grained, dark gray, 

 somewhat laminated, and shows scattered throughout its mass 

 abundant black spherules in varying sizes up to five millimeters. 

 These are a trifle rough on exterior surfaces, but break away easily 

 from the matrix leaving smooth cavities often lined with a portion 

 of the exterior shell of the spherule. In thin section they are plainly 

 fragmental, and show a thin outer zone or border of fine, dark material 

 enclosing the coarser, clastic silicate particles (see fig. 2, pi. 31) which 

 form the general groundmass of the stone. The structure on the 

 whole so closely simulates that of the "fossil rain drops" noted 

 elsewhere, as to suggest a lUve origin for both. Be this as it may, 



13 Zeit. fur Vulkanologie, vol. 1, Heft 1, 1914. 

 i< American Geologist, vol. 11, 1893, pp. 269-271. 

 i« Bull. Qeol. Soc. Amer., vol. 15, no. 2, 1924, p. 335. 



