4io 



NATURE 



[September 28, 191 1 



would not seem to be due to utilitarian causes, but 

 rather to an artistic tradition. This is interesting in 

 itself, but it also has a bearing on another point, 

 perhaps even more interesting. On p. 162 of vol. i. 

 is a curious group of chipped implements, some of 

 them in the form of human profiles, while others are 

 axes with curved sides expanding to a crescent-shaped 

 cutting edge. It is well known that in passing from 

 the use of stone to that of metal (often copper) the 

 earliest metal axes are accurate copies of the stone 

 type. Experience soon showed that hammering of 

 the copper edge not only sharpened it, but, very 

 naturally, widened it also, so that the natural result 

 of the process was to produce a rounded cutting edge, 

 with a curve from its two sides towards the butt. This 

 resulting form, being at once more practical and more 

 elegant, in turn became the type of copper or bronze 

 axe. 



These two facts, the presence of Mexican stone 

 types, as well as types founded on a cast-metal proto- 

 type, in American Indian settlements, may well lead 

 one to consider whether both one and the other had 

 an origin further south than the United States. It 

 may be contended that copper implements are common 

 enough in the United States, and that there is no 

 need to look further. But it is not of so much import- 

 ance that the prototype should be of metal ; it is that 

 it should be of cast metal. 



These are some of the many questions that are 

 raised by the perusal of Mr. Moorehead's elaborate 

 work. We can congratulate him on its encyclopaedic 

 character, a useful feature. The amount of material 

 is amazing, and the exquisite implements from Ten- 

 nessee in the Missouri Historical Society's museum 

 will be a surprise to most people on this side. We 

 could have wished that he had placed his figures 

 somewhat nearer the text relating to them, and that 

 his index had been a little better. 



THE VULCANICITY OF OUR EARTH. 

 Die vulkanischen Erscheinungen der Erde. By Dr. 



K. Schneider. Pp. viii + 272. (Berlin: Gebruder 



Borntraeger, 191 1.) Price 12 marks. 

 "TAR. SCHNEIDER opens his work by reference to 

 ■L' what is found in many books on vuleanology 

 and geology, namely, the part played by volcanic 

 activities in the economy of nature. In consequence 

 of volcanic action minerals of high specific gravity are 

 brought to the surface, the contours between land and 

 water may be changed, and new islands may be 

 created. Since Tertiary times 396 mill, km. 2 of land 

 surfaces have been covered by volcanic ejecta. These 

 accumulations have altered relative altitudes, on which 

 climate, plant life, and other things depend. Valleys 

 have been blocked, lakes formed, and river courses 

 have been changed. At the time of an eruption a 

 variety of gases and chemical products arc brought to 

 the surface, and many mineral deposits are closely 

 associated with volcanic action. Although in many 

 ways volcanoes have been beneficial to humanity, in 

 their immediate vicinity they have been frequently 

 associated with the loss of life and property. Volcanic 

 explosions have excited the imagination, given rise to 

 NO. 2187, VOL - 87] 



myths concerning subterranean deities or monsters, 

 and indirectly have had an effect on literature and art. 



At present we are told that on the surface of our 

 world there is one active volcano to 14204755km. 2 



We can regard volcanoes from a geographical, 

 petrographical, chemical, and other points of view, 

 and what has been done in each of these directions 

 is briefly reviewed. The notes relating to the tempera- 

 tures of lava and the average depth at which a rapid 

 change might be expected in materials similar to 

 those we meet with on the surface of our earth might 

 easily have been extended. 



Dr. Schneider's classification of volcanoes depends 

 on their forms, and of these there are seven types. 

 The names given to these types were quite as startling 

 to me as was the word anhydrohepsepterion when I 

 first heard it. It turned out to be a saucepan in 

 which vou can cook potatoes without water. 



Pedioniten are fissure outflows like the Deccan 

 Traps. Aspiten are characterised by the relationship 

 of their height to an extended base, as, for example, 

 Mauna-Loa. Tlioloiden refer to forms with a gentle 

 sloping base which runs inland from a coast and then 

 suddenly rises with convex flanks to a rounded summit. 

 Beloniten are illustrated by the needle-like peak of 

 Mount Petee. Koniden : these are mountains the 

 flanks of which are convex-concave. A slight reference 

 is made to this logarithmic curvature of volcanic profile 

 which was first noticed in connection with Mount Fuji, 

 but the lesson it teaches respecting the height of a 

 mountain and the area of its base in relation to the 

 material out of which it is formed, has apparently 

 escaped notice. The relation of form to the size of 

 ejectamenta, friction, wind, and the character of an 

 eruption has not been overlooked. Homaten. In 

 these the slope rises directly from the coast to the 

 summit as in Hverfjell in Iceland. Maare. Here the 

 volcanic neck has risen to the surface, clastic material 

 has been spread widecast, and flat hollows have been 

 created similiar to those in the crater lakes in the 

 Eifel. Each of these types can also be found in the 

 moon, and on our earth consists of materials with 

 different physical structures. Rheumatitische material 

 is that which flows like lava. The other materials 

 may be clastic like lapilli and ash, gaseous and 

 aqueous. Tertiary volcanoes are characterised by the 

 prevalence of materials first referred to, whilst the 

 materials of recent volcanoes are more clastic. 



A chapter of considerable interest to geologists is 

 one which gives an outline of vocanic action in Europe 

 since Tertiary times. This, however, does not en- 

 tirely overlook the vulcanicity which took place in 

 earlier periods. The number of active volcanoes in 

 the world during the Diluvium-alluvium period is 

 estimated at 10S1, whilst during historical times only 

 201 can be counted. These latter are grouped along 

 great lines of dislocation in the larger features of the 

 earth's crust. They do not occur in rows, but in 

 relatively small zones. These are two out of eight 

 laws formulated in connection with the geographical 

 distribution of volcanoes, which is illustrated by 

 numerous maps. The volume concludes with a cata- 

 logue oi 367 volcanoes which have been active during 



