192 Notices respecting New Books, 



smaller reflecting power can be got over by using a trans- 

 parent scale with opaque lines backed by a flame, in place o£ 

 the ordinary opaque scale illuminated by diffuse light. 



Platinum mirrors appear as if they might be of considerable 

 use where a metallic mirror is required, and where silver 

 would be likely to tarnish. When glass is used considerable 

 care has to be used, in the first place not to increase the 

 temperature so quickly as to crack the glass, and secondly 

 not to raise the temperature to such a height as to alter the 

 figure of the glass by softening. When crystalline quartz is 

 used no softening is to be feared. The temperature has, 

 however, to be altered very sloicly or the quartz will crack. 

 With care, however, very perfect mirrors have been obtained 

 on quartz. 



Platinum deposited in this way forms a very good coating 

 for producing "half-silvered'^ mirrors for use in interference 

 experiments and such instruments as those recently described 

 by Sir Howard Grubb (Sci. Trans. R. Dublin Soc. vii. 

 p. 385, 1902). The preparation of a surface having a given 

 reflecting power is much easier in the case of platinum than 

 in the case of silver^ and once such a surface has been 

 obtained it seems to be practically unalterable. 



XXIII. Notices respecting New Books. 



International Catalogue of Scientific Literature. First Annual Issue. 

 C. Physics. Part I. London : Harrison and Sons. 1902. 

 Pp. xiv + 239. 



A S a ready means of ascertaining everything of importance that 

 ■^^^ has been published on any particular subject of scientific 

 inquiry, the new International Catalogue of Scientific Literature 

 should prove of inestimable value to all engaged in original 

 research. The present volume, which refers to Ph^^sics, contains 

 schedules and indexes in four languages, an authors' catalogue, 

 and a subject catalogue. The arrangement adopted should enable 

 any one to find the particular section required without any 

 trouble. 



Subject List of Works on General Science^ FTiysics, Sound, 3Iusic, 

 LigJit, Microscopy, and Philosoplncal Instruments, in the Library 

 of the Patent Office. London: Patent Office. 190:5. Pp. 183. 



This catalogue of books on physical subjects will be found useful 

 by all who are in the habit of frequenting the Patent Office 

 Library. 



