Reviews — J. F. Whiteaves — Presidential Address. 137 



In none of the areas in which these bombs occur is there any 

 indication of either active or extinct volcanoes, and the question of 

 their distribution is a problem which the author does not attempt to 

 solve. 



The specimens all consist of a black compact and homogeneous 

 glass, with a very few small and isolated gas inclusions, but no 

 crystals of any kind. The specific gravity varies between 2-4:1 and 

 2-52. There is no doubt that the bombs are xen\\^ of Obsidian, and 

 that they are volcanic in origin. One specimen is polyhedral in 

 form, others are rounded or ellipsoidal, with the peculiarity that 

 they appear as if built up of two distinct halves, one somewhat 

 flattened and larger, the other more convex and smaller. In two 

 instances the form is that of a button-shaped mushroom ; as if the 

 smaller of two rounded thick-walled shells had been pressed into 

 the concavity of the larger. One specimen is a hollow sphere, 

 which may have been simply a large babble enclosed by glassy 

 walls. In this hollow bomb and in the mushroom-like forms 

 there are on the larger and flatter hemisphere, and on this only, 

 from four to six ring-like elevations parallel with the equatorial 

 margin, as well as fine straight or wavy lines, having a meridional 

 direction ; and further, this flatter half has a distinctly varnished 

 appearance in contrast with a dull aspect on the other more convex 

 half of the bomb. 



The peculiar form of these bombs, and the pittings and other 

 markings on their surfaces, are attributed to the resistance which 

 they encounter in their flight through the atmosphere, and their 

 individual difl'erences probably depend on the greater or lesser 

 plasticity of the lava when the explosion takes place, and the 

 varying rapidity of the projectile and the consequent varying force 

 of the resistance of the atmosphere. The bombs examined range 

 from 15 mm. to 55 mm. in their greatest diameter. 



III. — 1. Presidential Address : The Cretaceous Systebi in 

 Canada. By J. F. Whiteaves. (Transactions of the Eoyal 

 Society of Canada, Section IV. 1893, pp. 3-19.) 

 2. Note on the Recent Discovert of Large Unio-like Shells 

 IN the Coal-measures at the South Joggins, Nova Scotia. 

 By J. F. Whiteaves. (Transactions of the Eoyal Society of 

 Canada, Section IV. 1893, pp. 21-24.) 

 1, ri^HE first of these papers contains an interesting summary of 

 1 the Cretaceous system of Canada from the palaeontologist's 

 standpoint, and as it proceeds from the pen of one of the best 

 authorities on the American Mesozoics the views put forth in it 

 carry weight. 



The literature of the subject dates from the year 1857, at which 

 time F. B. Meek, that most accomplished of American paleon- 

 tologists, described some fossils from the Cretaceous rocks of 

 Vancouver Island (Trans. Albany Institute), and in the same 

 year Dr. J. S. Newberry discussed the age of the rocks associated 



