SCIENCE 



^•aJii-JiJj 



New Series 



Vol. LVI, Xo. 1443 



Friday, August 25, 1922 



Annual Subscription, $6.00 

 Single Copies, 15 Cts. 



The MacLeod Vacuum Gauge 



Columbia University Modification 



Besides retaining the features of the original Mac- 

 Leod gauge, namely: Ease of reading and accuracy 

 to one ten millionth of an atmosphere, the Columbia 

 University modification, (see cut), is easier to manip- 

 ulate, simpler, smaller, more compact, and without 

 ground joints. 



Price of the improved form with sliding mm. scale, 

 rack, and pinion support and adjustment for 

 levelling bulb, vnthout mercury $37.50 



American Rotary Vacuum Pumps have the follow- 

 ing advantages: Compact; operate with small ex- 

 penditure of power; require no attention when in 

 operation; not affected by chemically active gases; 

 not endangered if vacuum is broken. 



ISTo. 1 — Capacity 5 cu. ft. per mm. Pressure limit 

 1/50" of mercury. Recommended for general labo- 

 ratory work. 



No. 11/2 — Used with a supporting pump for exhaust- 

 ^^ing the bulbs of tungsten lamps and similar work. 



No. 2 — Used with supporting pump for high 

 vacua as required in X-ray work. 



Write for new bulletin No. 288 which ^ves details 

 of above apparatus 



mETid 



NEW YORK CITY 

 3rd Ave., 18th — 19th St, 



PITTSBURGH BRANCH 

 4048 Jenkins Arcade 



ESTABLISHED 18S1 



Headquarters for Laboratory Apparatus and Chemical Reagents 



Washington, D. C. Display Room, Suite 601, Evening Star Building, Pennsylv 



nd nth Street. 



