FROM NEAR LAKE AINSLIE, N. S. POOLE. 348 



tion which apparently took place in the crust of our Ainslie 

 bombs under consideration. Another extract from the writings- 

 of an authority on volcanic rocks I make as apposite to the 

 question at issue. Professor I. C. Russell, writing on the 

 eruptions on Martinique in 1902, says — ■" In addition to the 

 angular fragments of fresh lava, minor quantities of more or 

 less spherical masses of similar material, which were projected 

 into the air while yet moderately plastic, have also been 

 observed. While the term volcanic bomb has been applied to 

 much of the ejected material, it is evident that only the some- 

 what spherical masses referred to deserve to be so called, and 

 even in such instances there is doubt as to the propriety of 

 using the term. Typical volcanic bombs have a round or oval 

 form with extended and spirally twisted projections at the ends 

 of the longer axis, the spherical or more commonly oval form 

 and the spirally twisted extremities being due to the rotation 

 of the mass during its serial flight and while yet plastic. 

 The nearest approach to a characteristic bomb are certain rudely 

 spherical masses of lava with cracked surfaces and without 

 protections to which have been given the name of Breadcrust 

 volcanic bombs. Evidently these poorly shaped bombs are 

 composed of fresh lava which was sufficiently hot to make it 

 somewhat plastic at the time it was blowai into the air, but was 

 too rigid to acquire the typical shape frequently to be seen 

 about certain basaltic craters. The absence of characteristic 

 bombs on Martinique and St. Vincent is in keeping with the 

 composition of the lava thrown out. The fresh lava is an 

 andesite having in a general way the composition of refractory 

 brick, and unless very highly heated would not be plastic. 

 Not only are true volcanic bombs absent, but dots and splashes 

 of plastic or fluid rocks such as are common about many vol- 

 canoes that have erupted easily fusible material are also lacking." 

 In the case of the Ainslie bombs, the composition is more 

 acidic than andesite, and there is an entire absence of fusion in 

 the mass, without any trace being observed of the spiral pro- 



