SCIENCE-ADVERTISEMENTS 



Fuel 



Solid, Liquid, and Gaseous 



By J. S. S. BRA.ME, P.C.S., Instructor in Chemistry, Royal Naval College, Greenwich, Lecturer on 



Fuel, Sir John Cass Technical Institute, Aldgate. With 73 Figures and 55 Tables. 



8vo. Pp. xvi+372. $3.50 net. (Weight, 34 oz.) 



Endeavor has been made in this book to place before the technical man, who is not a fuel 



specialist, but who requires a good general knowledge of the subject, as full information on all fuels 



of importance as space permits : at the same time the scientific principles underlying gas producer 



practice, combustion, etc., have not been neglected. The application of fuels to other purposes has 



not been overlooked, but primarily fuels are considered in their relation to power. As far as possible 



the diagrams have been chosen to illustrate principles and typical forms of plant and apparatus. 



Geological and Topographical Maps 



Their Interpretation and Use : A Handbook for the Qeologist and Civil Engineer 



By ARTHUR P. DWERRYHOUSE, D.Sc, F.G.S., Lecturer in Geology in the Queen's University of 

 Belfast. With 90 Figures and 2 Tables. 8vo. Pp. viii+133. $1.25 net. (Weight, 18 oz.) 

 A text-book dealing with the practical problems which are involved in the interpretation of maps, 

 descriptions and instructions that will enable the civil engineer and the student of geology to draw 

 sections of the country depicted upon maps, and to ascertain the depths and thickness of the various 

 strata of which it is built up, and their relations to the surface of the ground and to each other. 



A brief summary of the main structural features of rooks is included, for the benefit of those un- 

 able to obtain a systematic course of instruction in geology. 



Longmans, Green, & Co. 



4th Ave. & 30th St., N. Y. 



LEITZ NEW COMPARISON EYEPIECE 



This Comparison eyepiece 

 serves for comparing, by 

 means of a simple ocular, 

 two objects on the stages 

 of two different micro- 

 scopes arranged side by 

 side. The usual type of 

 microscope available in 

 the laboratory may be 

 utilized, and it is essential 

 that only objectives of 

 identical power and optical 

 data are used. 



Manipulation 



Under one of the micro- 

 scopes utilized, a normal 

 (standard) specimen is 

 placed whil e th e other stand 



Write for Lit 

 erature 71 O. 



Leitz Compari- 

 son Eyepiece, as 

 described, $36. 



holds the preparation to be 

 compared, in order to de- 

 termine if any coincidence 

 in the specimens exists. 

 The two images in the 

 field are situated side by 

 Bide, so that every mioro- 

 scopist will realize how 

 reliable such a comparison 

 is bound to be. 



Construction 



The ocular consists of a 

 prism casing with two 

 tubes attached thereto. 

 These tubes slip into the 

 draw-tubes of the two mi- 

 croscope stands. 



Board of Health Departments, especially, compelled daily to investigate food and other preparations in 

 order to determine if same comply with the Pure Food Act, will, in establishing a normal (standard) speci- 

 men, be in a position to make a proper analysis more readily and conveniently than heretofore. 



We are confident that this newjdevice of Comparison Ocular will assist greatly in proper microscopical 

 analysis and certainly answers a long-felt demand. 



UNITED STATES 

 BRANCH 



E.LEITZ 



^Etz^I 



30 EAST 18th ST. 

 NEW YORK 



