D. VAST ITOSTIIA&D. 23 



Mitchell s Manual of Assaying. 



8vo. Cloth. $10.00. 



A MANUAL OF PRACTICAL ASSAYING. By JOHN MITCHELL. 

 Third edition. Edited by WILLIAM CKOOKES, F.R.S. 



In this edition are incorporated all the late important discoveries in Assay 

 ing made in this country and abroad, and special care is devoted to the very 

 important Volumetric and Colorimetric Assays, as well as to the Blow-Pipe 



Assays. 



Benet s Chronoscope. 



Second Edition. 



Illustrated. 4to. Cloth. $3.00. 



ELECTRO-BALLISTIC MACHINES, and the Schultz Chrono 

 scope. By Lieutenant-Colonel S. V. BENET, Captain of Ordnance, 

 U. S. Army. 



CONTENTS. 1. Ballistic Pendulum. 2. Gun Pendulum. 3. Use of Elec 

 tricity. 4. Navez Machine. 5. Vignotti s Machine, with Plates. 6. Benton s 

 Electro-Ballistic Pendulum, with Plates. 7. Leur s Tro-Pendulum Machine 

 8. Schult/ s Chronoscope, with two Plates. 



Michaelis Chronograph.. 



4to. Illustrated. Cloth. $3.00. 



THE LE BOULENGE CHRONOGRAPH. With three litho 

 graphed folding plates of illustrations. By Brevet Captain E. 

 MICHAELIS, First Lieutenant Ordnance Corps, U. S. Army. 



&quot; The excellent monograph of Captain Michaelis enters minutely into the 

 details of construction and management, and gives tables of the times of flight 

 calculated upon a given fall of the chronometer for ail distances. Captain 

 Michaelis has done good service in presenting this work to his brother officers, 

 describing, as it does, an instrument which bids fair to be in constant use in 

 our future ballistic experiments. Army and Navy 



