

BAUSCH & LOM 



ICROSCOPES 



BS 



Revised and Reduced Prices. 

 MANY IMPROVEMENTS. 



Over 81)000 have been sold and are in use. 



Tfcert art no tutttr Instrument* mads for Colleges or Laboratories. 



THE NEW B.H. MODEL 



(illustrated) is completely redesigned. Larger and heavier stand, 

 longer draw-tube, larger stage (will take full size Petri dish), im- 

 proved iris diaphragm, substage, with_ screw-out or new screw- and 

 swing-out fitting, fine adjustment giving slow or rapid movement, 

 very solid rack and pinion. From £5 14s. 6cJ. 



Complete Bacteriological Outfit, £13 9s. 6d. 



Also Microtomes, Centrifuges, Photomicrographic and 

 Projection Apparatus, Vlscoslmeters, Precision Labora- 

 tory Glass Ware, etc. 



THROUGH ALL DEALERS. 



Inspection cordially Invited at our Showrooms, or Lists sent post tree. 



THE BAUSCH & LOMB OPTICAL CO., 



Contractors to British, Indian, Colonial, and Foreign Governments, 



trademark. 19, THAVIES INN, HOLBORN CIRCUS, LONDON, EC. 



THE GREAT STAR MAP 



BY H. H. TURNER, D.Sc. F.R.S. 



Sarilian Professor of Astronomy in the University of Oxford. 



Crown 8oo. 2s. 6d. net. 



[Just out. 



In 1887, an International Conference at Paris determined to map the places of 

 all stars in the heavens brighter than a certain standard by photographic means. 

 The work has proved far more serious than was at first anticipated, and is not 

 yet accomplished. It involves the taking of 20,000 photographs, and the 

 measurement of 8 or 9 million star images. It was divided among 18 observatories, 

 and two of these, Greenwich and Oxford, have practically completed their por- 

 tions. Professor Turner, who has superintended the Oxford work, gives a brief 

 popular account of the scope of the work, and of the problems which it will 

 assist in solving, with incidental references to recent discoveries which concern 

 the constitution of the universe of stars. 



JOHN MURRAY, ALBEMARLE STREET, W. 



( xvi ) 



