Nsw Sekiks 



Vol. LVI, So. 1-iGO 



Friday, December 22, 1922 



ANNTTJaI.. SlTBSCEIPTION, $6.00 



Single Copir.B, 15 Cts. 



The MacLeod Vacmim Gauge 



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, without 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. 



No. 1 — Capacity 5 cu. ft. per mm. Pressure limit 

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

 ratory work. 



No. 1% — Used with a supporting pump for exhaust- 

 ig 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 bunetin No. 28S which gives details 

 of above apparatus. 



NEW YORK CITY 

 3rd Ave., 18th — 19Uj St. 



PITTSBURGH BRANCH 

 4048 Jenkins Arcade 



ESTABLISHED 18S1 



Headquarters for Laboratory Apparatus and Chemicals 



Washington, D. C, Display Room, Suite 601, Evening Star Building, Pennsylvania Avenue and 11th Street. 



