D. VAJST NOSTRAND. 23 
Mitchell’s Manual of Assaying. 
8vo. Cloth. $10.00. 
A MANUAL OF PEACTICAL ASSAYING. By John Mitchell. 
Tliird edition. Edited by William Crooke.s, F.E.S. 
In this edition are incorporated all the late important discoveries in Assay 
ing made in this country and ahroad, and special care is devoted to the very 
important Yolumetric and Colorimetric Assays, as well as to the Blow-Pipe 
Assays. * 
Benet’s Chronoscope. 
Second Edition. 
Illustrated. 4to. Cloth. $3.00. 
ELECTEO-BALLISTIO MACHINES, and the Schultz Chrono- 
scope. By Lieutenant-Colonel S. Y. Benet, Oaptain of Ordnance, 
U. S. Army. 
Contents.—1. Ballistic Pendulum. 2. Gun Pendulum. 3. TJse of Elec- 
tricity. 4. Navez’ Maehine. 5. Vignotti’sMachine, with Plates. 6. Benton’s 
Electro-Ballistic Pendulum, with Plates. 7. Eeur’s Tro-Pendulum Maehine 
8. Schultz’s Chronoscope, with two Plates. 
Michaelis’ Chronograph. 
4to. Illustrated. Cloth. $3.00. 
THE LE'BOIILENGE CHRONOGEAPH. With three litho- 
graphed folding plates of illustrations. By Brevet Captain 0 E. 
Michaelis, Eirst Lieutenant Ordnance Corps, U. S. Army. 
“ The excellent monograph of Captain Michaelis enters rainutely into the 
details of construction and management, and gives tables of the tim es of ■flight 
calculated upon a given fall of the Chronometer for all 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 Ndvy Journal.