Thb Davoh" Patcnt 



I 



^^J^lcrcfr^/escope 



combines the functions of the microscope, telescope, camera and pro- 

 jecting lantern for laboratory, educational, and industrial purposes. 



THE GAP BETWEEN THE MICROSCOPE AND TELESCOPE IS BRIDGED. 



TERRESTRIAL OBSERVATIONS from six feet to infinity. Mag- 

 nifications 16 — 50. Objects which because of their size or shape 

 {e.g., insects, plant life, eggs, &c.) cannot be put upon the stage of a 

 microscope, can be viewed at from three feet to one foot distance, 

 magnifications x 30—90. ALL IN STEREOSCOPIC RELIEF. 



IDEAL FOR POND LIFE AND NATURE STUDY. 



" Your exhibit on pond life was the ' piece de resistance.' 

 It was a revelation and astounded all." — Leeds University. 



GREAT DEPTH OF FOCUS both visually and photographically. 



TELE-PHOTOGRAPHY. With any plate camera. Magnification 

 20 diameters, covering J-plate, with 10' extension. 



THE "DAVONTEL," Price £12 12 0. It takes the place of the 

 camera lens. Photos have been taken at distances varying from 

 6 feet to 70 miles. Fine photos of birds' nests, some in autochrome, 

 were taken by Dr. Wright, of Crossgar, Co. Down. 



Illustrated descriptive brochure free from : — 



F. DAVIDSON & Co., "*SS?ft?iISi:''° 



29, GREAT PORTLAND ST., LONDON, W.I. 





Agsnts .—Sheffield, WALLACE HEATON, LTD., Change Alley. 

 Manchester, G. WOOLASTON, Lord's Chambers, Corporation Street. 



SCIENCE PROGRESS 



A Quarterly Review of Scientific Thought, 

 Work and Affairs. 



Editor - COLONEL SIR RONALD ROSS, K.C.B., F.R.S. 



This Quarterly is now in its fourteenth year of pubHcation. Its 

 object is to give all readers of wide culture and interest in science 

 a knowledge of the numerous advances which are being continually 

 made in connection with scientific work and thought. Each number 

 contains Recent Advances in Science (by a number of experts), 

 Articles, Popular Science, Essay-Reviews, Correspondence, Notes, 

 Essays, many Reviews, and a Book List. Published early every 

 quarter by John Murray, 50a Albemarle Street, London, W. Annual 

 Subscription 25/6 and price of one number 6s. Subscriptions 

 through bookseller or direct to the Publisher. 



" Science Progress, which has now reached its thirty-ninth 

 number, not only covers a remarkable wide field with great 

 ability, but has had impressed upon it, by the energetic and 

 humane spirit of its editor, a certain dynamic quality which 

 makes it a force as well as a source of light." — The Times, 



Printed at Browns' Savile Press. 40 George Street, Hull, and published by 

 A. Brown & Sons, Limited, at 5 Farringdon Avenue, in the City of London. 



Jan. 1st, 1921. 



