TRANSACTIONS 



OF THE 



^oba ^cottan Jii^titutc of .Science, 



^^ 



SESSION OF 1904-1905. 



Pre-Cambriax Volcan^ic Bombs from near Lake Ainslte, 

 In'verness Co., X. S. — By Henrv S. Poole, d. sc, assoc. 



R. S M., F. G. S., F. R. S. C. 



{Read 17th Octohzr, WOi.) 



Among the I'ocks of Cape Breton, X. S., classed in the 

 Report of the Geological Survey of Canada of 1882-4 as pre- 

 Carabrian, in a deposit on the east side of Lake Ainslie, are 

 some globular balls associated with modified forms presenting 

 marked features. They differ in so many respects from con- 

 cretions ordinarily seen taking spherical shape in sandstones, 

 plaster and shales, that these balls could not be grouped with 

 them and thus dismissed. It may first be noted they are found 

 with pyroclastic rocks, and next that such concretionary 

 structure as they do present is in most cases merely superficial ; 

 they are associated in a bed which has cavities coated with 

 matter that has flowed while in the condition of thick mud or 

 paste and retained the forms then taken as ridges and layers 

 of varied consistency. The balls have an indurated appearance 

 with a smooth surface, and vary in size from that of a pin's 

 head to a cricket ball. Rarely over three inches in diameter, 

 the largest seen was a flattened oval of 7 in. by 5 in. by 3 in. that 

 apparently had lost, through impact or pressure on contact with 

 Proc. & Tran-s. X. S. Inst. Sci , Vol. XI. Trans. W. 



(339) 



