408 SUMMARY OF CURRENT RESEARCHES RELATING TO 



as in the tube above. At the bottom of the drain-pipe is a short 

 removable section (fig. 43, g) to which a piece of rubber tubing can be 

 attached to carry the waste to a convenient receptacle. The doors are 

 fitted with metal finger-pulls (fig. 43, h) for convenience in sliding, 

 and two metal handles are attached at the top for lifting the box. The 

 whole is painted inside and out with a dull black shellac. It stands on 

 a small table, in which there is a hole to permit the passage of the 

 drain-tube. I have found the most convenient height of the table for 

 use with an ordinary chair to be 2 ft. In the field a box or two chairs 

 serves very well for a support in place of the table. 



When filling plate-holders, the box of plates and the holders are 

 placed in the dark-box and all openings closed. The workman sits with 

 his arms in the sleeves, which are pulled well on at the wrists, and fills 

 the holders in perfect comfort. 



In developing the plates, the plate-tank containing the developer, 

 the plate-cage and the plate-holders are placed in the box as before. 

 When the cage, containing the plates, is safely in the closed tank, the 

 box can be opened until the developing is done, when the tank is 

 returned to the box, where the developer is poured off through the 

 drain (fig. 43, c). The plates are then washed in several changes of 

 water, which is drawn from the faucet (fig. 43, s) ; then they can be 

 taken to the light of the room and placed in the fixing-bath. 



The box as described is a convenient size for use with 4x5 and 

 5x7 plates. With a 5 x 7 plate-tank it would be well to make the 

 water-tank slightly larger. 



(6) Miscellaneous. 



Manual of Petrographic Methods.*— This book removes a long- 

 standing reproach to English Petrography. It is, as is stated in the 

 preface, " the first attempt to give in English a comprehensive review 

 of petrographic methods." The author has abundantly realized his aim, 

 and produced a book which, in our opinion, must long remain the 

 standard book of reference on petrographic methods in the English 

 language. It represents a colossal amount of literary research, which 

 will be appreciated when it is stated that more than 130 periodical publi- 

 cations, in some half a dozen languages— mainly, however, in English, 

 French, and German — are referred to. In addition, eight bibliographies 

 are given at the ends of as many chapters, together with copious re- 

 ferences in the form of foot-notes on nearly every page. 



The first twelve chapters of the book are of a more or less introduc- 

 tory nature, dealing as they do with general and crystallographic optics ; 

 the action of the various optical elements used in petrographic research 

 — more especially polarizing prisms — being very fully dealt with. The 

 various forms of petrological Microscopes, too, come in for a good share 

 of attention. Chapters XIII to XX deal principally with observations in 



* By Albert Johannsen, Ph.D., Assistant Professor of Petrology, University of 

 Chicago. New York and London : McGraw-Hill Book Co., Inc., 1914, xxviii. and 

 649 pp. (765 figs, in text). 



