FEBRUARY 22, I1917| NATURE cxcv 
SCIENTIFIC BOOKS 
Largest Stock in London of Text-books and 
Standard Works in all Branches of Science. 
BOOKS IN GENERAL LITERATURE ALSO SUPPLIED. 
“SPECIAL FACILITIES FOR EXECUTION OF ORDERS FROM ABROAD; 
effectually protective packing used without charge. 
136 GOWER ST.. 
LONDON, W.C. 
Metropolitan Railway: Euston Square Station. 
All Tube Railways: Warren Street 
Telegrams: “ Publicavit, Eusroad, London.’’ 
Telephone: Museum 1072. 
NOTICE. 
; For the convenience of readers of NATURE wishing to 
inspect books published abroad which have been reviewed 
in NATURE such volumes are kept for the period of six 
months at the publishing office of the Journal. The books 
; are retained for the purpose of examination free of charge. 
St. Martin’s Street, London, W.C. 
THE ARM OF THE 
Bausch [omb 
NEW HIGH - POWER 
BINOCULAR MICROSCOPE 
KD (described and illustrated in our advertisement in Natur, Dec. 28, 
1916) is eo constructed that the binocular body of our KA Microscope 
(Greenough Type) can be readily fitted thereto by the user, thus allowing 
either SINGLE OR PAIRED OBJECTIVES to be used on ihe 
same stand. The annexed illustration shows the substitution. 
The extra cost of the KA Body (including the fitting), with one pair 
of eyepieces and one pair of objectives, 40mm., in case, is £9 7 6 
—catalogue price, subject to 74% war advance. 
Microscopes for all requirements up to the most advanced research. 
Inspection invited at our Showrooms, or List ‘‘Al’’ (Microscopes 
and Accessories) sent post free. 
WE HAVE SOLD OVER 118,000 MICROSCOPES, WHICH ARE 
IN USE ALL OVER THE WORLD. 
Bausch & lomb Optical @.[td. cng ced, lnsion Colonel 
AGENTS FOR 
BAUSCH & LOMB OPTICAL COMPANY, of ROCHESTER, N.Y., U.S.A. 
37-38 Hatton Garden, London, E.C. 
Our Instruments may be obtained through all Dealers. TRADE MARK ° 
