SCIENCE-ADVERTISEMENTS 



Gaede Molecular Air Pump 



Made by E LEYBOLD'S NACHFOLGER This air pump oper- 



ates on an entirely new 

 and interesting princi- 

 ple. No mercury is 

 used. With a fore-vac- 

 nnra of .01 mm. it will 

 ( \acuate a 6-liter vessel 

 from 10 mm. to .00001 

 uiiii. in 3 minutes. It 

 pumps vapors as well 

 as gases, greatly sim- 

 plifying the process of 

 evacuation. 

 Gaede Molecular Air Pump with 110 V Motor and Regulator 



Write for Illustrated OescrlDtive Price List No. 6 



The Gaede Molecular Air Pump is Imported into the United States by 



JAMES G. BIDDLE 



1211-13 ARCH ST. Special Representative PHILADELPHIA 



When in Philadelphia be sure to visit our Permanent Exhibit of scientific apparatus. 



'* * ^ '«I5?^'''-'^l.-_'^4Jfc'M'' 



XJ. s. 

 Brancli 



"GREENOUQH LEITZ" 



Stereoscopic Image Erect= 



ing Microscopes 



Embodying a new type of construction 

 providing greater stability than in all 

 previously existing models. 

 Rigid adjustments of microscope tubps 

 with Porco Prisms is assured by the plac- 

 ing of rack and pinion independent of 

 such adjustments. 



Patented Elastic Prism Mountingr In 

 Steel Sprinsrs— lame as in our Prism Bi- 

 nocular Field Glasses. 

 Upper part of microscope with prism 

 tubes is removable, for attachment to a 

 special hard rubber foot (with indepen- 

 dent rack and pinion coarse adjust- 

 ment), serving conveniently in exami- 

 nation of large surfaces ( Dermatoscope 

 Arranffement.) 



Paired objectives mounted on self cen- 

 tering slides, and can be adjusted rela- 

 tively to each other. One objective in 

 focussing mount to overcome difference 

 of refraction between the observer's eye. 

 The " Greenoueh Leitz " is also made 

 in Foldingr Form, meeting a long felt 

 demand of those who require this in- 

 strument when in the field. Supplied 

 in a convenient sized morocco case. 



A'ik tor Uteratare SSY 



ISew York 

 30 East IStli St. 



