Geology and Mineralogy. 169 



of the Trias, for the forms characteristic of two great periods of 

 development meet in it; that is, the survivors of the past period 

 (Mesozoic) and the new forms of the approaching one (Tertiary). 

 This being true, we should expect to find in any large collection 

 of Neocomian plants a great mingling of types. We should find 

 the survivors of the old floras and the newly arrived precursors 

 of the more recent ones mingled with a number that attain their 

 development in and are peculiar to the Neocomian. This is 

 exactly what we find to be true of the Potomac flora. That so 

 many of these plants are new is perhaps to be explained, in 

 part at least, by the fact already mentioned, that the flora of this 

 epoch is very poorly represented and comparatively but little 

 known. It is not possible to say positively to what precise epoch 

 of the Neocomian the Potomac belongs. Its flora ranges from 

 the Wealden through the Urgonian, and probably includes some 

 Cenomanian forms." 



3. Eruption of Bandai-san. Transactions of the Seismologi- 

 cal Society of Japan, vol. xiii, Part ii. — We have here a republica- 

 tion of the paper of Sekiya and Kikuchi (noticed in a former 

 volume) on the remarkable eruption of Bandai-san in 1888, with its 

 plates, and also an important paper on the same subject by C. G. 

 Knott and C. Michie Smith. A point of general interest in the 

 observations discussed in the second paper relates to the condition 

 of the forests, especially those south and southeast of the place 

 of eruption. It is stated that the forests were subjected "not 

 merely to a hurricane of wind, but also to a fierce cannonading of 

 stones of all sizes from the tiniest grains to huge blocks." " The 

 cloud of stones, largely unchecked, in their on-rush, shot over the 

 ridge and down the steep slopes till the smaller gradients and 

 their own accumulation brought them to a stand." " That much 

 of it was launched horizontally so as to graze the surfaces of the 

 ridge and high level slopes is demonstrated by the nature of the 

 damage done to the trees." " To get some idea as to the heaviness 

 of this bombardment we counted the separate cuts and bruises on 

 the quarter of a square foot of the surface of a battered tree, 

 selected as a representative one ; a careful count gave 75," or 

 " 300 missiles to the square foot." " There is no reason to sup- 

 pose that the vertical projection was denser than the horizontal ; 

 on the contrary, there are good reasons for supposing that the 

 horizontal was the greater ;" in other words, " the amount pro- 

 jected at lower inclinations than 45° far exceeded the amount pro- 

 jected at higher angles." "As regards the larger fragments the 

 outburst was confined to inclinations less than 30° to the horizon- 

 tal." These facts seem to make it an explosive eruption in which 

 the explosion took place high up in the mountain. The mountain 

 had not been in eruption for 1000 years and had lost much of its 

 breadth in the meantime by erosion. The eruption was without 

 the medium in any way, according to Kikuchi (which is undis- 

 puted in the second paper), of liquid lavas. 



