January i6, 19 13] 



NATURE 



537 



BUILDING STONES. 

 (i) Handbuch der haiitechnischen Gesteinspriifung. 



Fiir Beamte der Materialpriifungsanstalten und 



Baubehorden, Steinbruchingenieure, Architekten 



und Bauingenieure, sowie fiir Studierende der 



technischen Hochschulen. By Prof. J. 



Hirschwald. Zweiter Band. Pp. xvi + 388-923. 



(Berlin: Gebruder Borntraeger, 1912.) Price 



32 marks. 

 (2) Building Stones and Clays: Their Origin, 



Characters and Examination. By Edwin C. 



Eckel. Pp. XV +264. (New York: J. Wiley 



and Sons; London: Chapman & Hall, Ltd., 



1912.) Price 125. 6d. net. 

 (i) ^ I "'HE first volume of Hirschwald's com- 

 _L prehensive work was noticed in Nature 

 of June 6, 1912 (vol. 89, p. 344). This, the 

 second and final volume, deals with the applica- 

 tion of the methods previously described. 



One of the outstanding features of Hirschwald's 

 method is the frank acknowledgment that different 

 types of stone demand that attention should be 

 paid to their peculiarities of structure and mineral 

 composition. Thus, he treats separately each of 

 the following types :- — Sandstones, grauwackes, 

 limestones — dolomites — marbles, roofingslates, 

 granites, gneiss with mica schists, syenites — 

 diorites — diabases, porphyries, trachytes — rhyolites 

 — andesites, basalts, schalsteins and tuffs. Under 

 each of these heads he gives an account of the 

 general petrographic characters, microstructure, 

 chemical composition, peculiarities of weathering, 

 special methods of testing applicable to the stone, 

 the mode of obtaining a valuation of the stone's 

 weather-resisting qualities from the results of 

 testing, and remarks upon the points to be 

 observed in the quarries. 



Microscopic examination he rightly regards as 

 of the first importance, and by its means the 

 structure and mineral composition of the stone are 

 analysed with great minuteness, and the results 

 of the examination are expressed in terms of 

 weather-resisting quality. This is done by assign- 

 ing a symbol to each recognisable degree of each 

 of the characteristics of stone structure, e.g., in 

 sandstones made of quartz grains bound by silice- 

 ous " cement " there are four grades : Ka, grains in 

 optical orientation with their neighbours ; KjS, 

 grains joined by outgrowths not so related; Ky, 

 microgranular quartz; KS, amorphous silica. 

 Then come thirteen grades of "contact cement" 

 other than simple silica. The pores in the stone 

 are treated separately; there are twenty-two 

 grades of "texture pores," empty or variously 

 filled, and as many grades of "structure pore" 

 types, and so on. Tables are given in which these 

 XO. 2255, VOL. go] 



symbols and the numerical results of physical tests 

 are assigned values according to a scale of weather 

 resistance which is itself the result of observa- 

 tions and tests made on tried stones actually 

 employed in buildings of considerable age. The 

 results of observation and test are added together 

 to obtain the desired figure representing the 

 quality (Q). This, for example, is the formula 

 i worked out for a certain sandstone — 



[ Kdpgk;ce Kb f,.a., Sr/V () 



I 0-52(2 -0-5) + 0-5 X i-5-o-5 + o-45= r45 = fl to II) 



indicating that the quality-class of the stone is 

 between first and second grade. 

 I The book provides fully worked-out tables and 

 I schemes for the valuation of microscopic observa- 

 tions and experimental results, so that by employ- 

 ing them it would be a comparatively easy matter 

 to obtain the formula for any new stone. 



At the recent congress of the International 

 Association for Testing Materials it was decided 

 to recommend that Hirschwald's method should 

 be tried and reported upon by testing institutions, 

 and to assist in this process a set of type micro- 

 slides and small samples of building stone with 

 annotations by Prof. Hirschwald will be procurable 

 from Krantz, of Bonn. 



(2) It is interesting to examine Mr. Eckel's new 

 work on building stones and clays side by side 

 with Hirschwald's book. The former is a well- 

 produced volume treating the subject on broad 

 lines and mainly from an American point of view. 

 The first two chapters are upon elementary 

 geology ; then follow eight chapters describing 

 the geological, chemical and physical properties 

 of the principal stone groups ; one on the field 

 examination and valuation of stone properties, and 

 one on the laboratory testing of stone. Part ii., 

 the short section on clays, is inadequate and 

 rather out of place nowadays in a book on build- 

 ing stones. 



The book contains much plain common sense, 

 together with what can be regarded only as 

 padding; thus, on p. 42 the author makes it 

 clear that commercial analyses of granite are of 

 little or no use, yet he immediately introduces 

 twelve pages of analyses. There are more than 

 thirty-eight pages of compiled analyses in the book 

 and a number of tables of physical test results 

 quoted from various sources. The latter are of 

 small value because, as the author himself well 

 knows, the tests are not made under comparable 

 conditions. Though much of the tabulated matter 

 might have been omitted without loss, the writer's 

 outlook, as a practical engineer, on the testing 

 problem is well worth consideration. 



The restricted American scope of the work is 

 illustrated by the scant notice taken of the 



