526 



NA TURE 



[June 30, 1910 



our desire to be untechnical, building^ in these matters 

 without foundations, and was not Huxley's original 

 scheme of " Physiography " a really sound guide to 

 nature-study, even if it made its appeal to children 

 somewhat older than those contemplated in the work 

 under review? 



Prof. Watts, at any rate, agrees with Huxley, and 

 presupposes, in his geological section, a knowledge 

 of the fundamental constituents of the earth. He 

 refers freely to "silica," "carbonic acid," "minerals," 

 "mica," and even " hydrated silicate of alumina." 

 After all, is there more in this than is expected of 

 the child when he is told to take one quart of milk to 

 James Stewart of Auchencairn and one pint and a 

 half to Mistress Campbell of Drumochter? The milk, 

 the persons, and the farms are realities to him, and 

 are therefore easy of comprehension. Is there any 

 objection to making him equally well acquainted with 

 the fundamental materials of the land ? Prof. Watts 

 gives the teacher the essential conceptions of geology, 

 and leaves him to select what is suited to the com- 

 prehension of his class. His style is terse and vivid, 

 and the illustrations selected by him, often from the 

 photographs of Mr. Godfrey Bingley, are in every 

 way worthy of the text. Since the principles of 

 geology are so greatly concerned with the form of 

 the earth's surface, the making of maps and models 

 is included in the course, and the use of the plane- 

 table, so attractive to beginners in geography, is 

 explained and illustrated. Several of the technical 

 terms in the chapter on the geological record, 

 " brachiopoda," for instance, are not included in the 

 index to the six volumes of the work ; but the author 

 moves on without hesitation — the teacher who under- 

 takes the geological branch of nature-study must be 

 ready to explain such technicalities to his class. Alto- 

 gether, we cannot conceive a more effective introduc- 

 tion to geology than is here put forward. 



To make two small criticisms, in the diagram on 

 p. 210 the relations of the upper series of beds seem 

 unnecessarily complicated by a surface-creep towards 

 the valley on one side ; and the chapter headed 

 " Igneous Rocks " is mainly concerned with clastic 

 rocks and earth movement. Since the conclusions 

 stated are drawn from observation in our own islands, 

 glaciers and volcanoes are more lightly treated than 

 in many popular works. Prof. Watts has not gone 

 out of his way to be popular, and has succeeded in 

 being so in the highest of all senses. 



Prof. W^alther, in his "Vorschule der Geologic," 

 has set much the same goal before himself. In five 

 years his simple little book has run into four editions, 

 and still forms a treatise that can be easily slipped 

 into the pocket. The author is one of a band of 

 German leaders in education who wish to see geology 

 taught in all secondary {hohere) schools. He here 

 leads on his reader to observe nature out of doors, 

 and in a number of practical exercises shows the 

 varied activities and changes on the surface of the 

 earth. His diagrams are equally simple and con- 

 vincing, whether of a tree forced to modify the form 

 of its stem through the down-creep of a talus (p. ii), 

 or of the formation of a granite tor (p. 29) by suc- 

 cessive stages of decay. Even Dr. Newbigin would 

 shake her head over Prof. Walther's rain-gauge 

 (p. 42) ; but his charming directness of style gives 

 one great confidence in his experiments. He permits 

 us chemical formulae, and even crystallographic 

 systems ; yet his work is quite unlike the text-books 

 familiar in German schools. His little local sketches, 

 such as the section of a swampy area in Fig. 30, are 

 real lessons in geography ; indeed, we have shown 

 these pictures to a class in the field in explanation 

 of the broad features of a landscape. We may differ 



NO. 2122, VOL. 83] 



with him on small points, such as his treatment o 

 trough-faulting, which surely arises most frequentl} 

 through the faulting of a fault by one of opposit< 

 hade ; but he guides us onward from our first observa 

 tions on a hillside until we can grasp the complexitiei 

 of a geological map. He expects us to purchase on* 

 and use it, and supplies index maps for all tli' 

 German surveys, with considerable lists of literature t( 

 assist our summer holidays. This confidence in th( 

 attractiveness of his subject is one of the charms o 

 Prof. Walther's treatise; but we must remember tha 

 he appeals to pupils trained by longer working hour 

 than our own, and to the sons and daughters of t 

 people that regards education with respect. 



Dr. Haas, in "Die vulkanischen Gewalten," add: 

 one more to Herre's series of popular scientific mono 

 graphs. The black-letter type, and occasional sen 

 tences in the long black-letter style, show that it i: 

 intended for general readers beyond the colleges. I 

 is not concerned with persona^ observation, but con 

 tains, logically stated, the results of a wide range o 

 research. The description of a volcano in time intro 

 duces us to earthquake problems and the constitutioi 

 of the earth's interior. Though the writers referrei 

 to are naturally for the most part German, the autho 

 has read widely, and even quotes (p. 97) Albert Brun' 

 view that the volcanic cloud consists of salts o 

 ammonia. This leads on to an interesting discussioi 

 of how volcanoes might be produced without th; 

 presence of water in the original igneous mass, an; 

 of Stiibel's theory of the formation of calderas bj 

 magmatic expansion and subsequent sinking of th 

 central areas. There is much in this "popular 

 work that will be useful to the teacher of geology 

 and the illustrations of dust-clouds and lava-flows ar 

 refreshingly recent, after the oft-repeated woodcuts 

 which we have become inured. 



Grenville a. J, Cole. 



THE MEDIUM OF CELESTIAL SPACE. 



THE phvsicist knows well that the problems wit 

 which he has to deal are insignificant, or 

 best subsidiary, when compared with the great que 

 tions so intimately connected. What is matter? an 

 What is aether? The astronomer, though he observ( 

 the operations of nature on a vaster scale, deals wit 

 problems of a less ultimate character. Thus, whe 

 he seeks to investigate the properties of that mediu 

 in which the solar system and the stars alike ai 

 moving, he is far removed from any metaphysic 

 abstraction, and only seeks the answer to perfect 

 definite, concrete questions concerning the tran 

 parencv and dispersive qualities of the medium. Bi 

 if the questions are concrete, they are by no meai 

 simple, and though the last two years have seen 

 simultaneous attack on the problem on several co 

 verging lines, the main result has been to make i 

 realise the immense difficulties which lie in the way 

 a definite conclusion. 



Whether there is a general absorption of light ^ 

 space, from whatever cause arising, is a point whi« 

 suggests itself most obviously. Without attributir 

 any absorptive power to the aether itself, it is easy 

 see' reason for inferring that a loss of light do 

 take place. The streams of meteors which enter o 

 atmosphere have not always been within the sphe 

 of influence of the solar system, but have probat 

 come in incalculable numbers from outer space. Th 

 is a continual drain on the atmospheres of the 

 and planets owing to the loss of the fastest-mov 

 molecules. The empty spaces which have been fou 

 to exist in the midst of the densest star clouds, and t 

 curious rifts which interrupt the continuity of cert 





I 



