40 SCIENTIFIC BOOKS PUBLISHED BY 



Saeltzer's Acoustics. 



12mo. Cloth. $2.00. 



TREATISE ON ACOUSTICS in Connection with Ventilation. 

 With, a new theory based on an important discovery, of facilitat- 

 ing clear and intelligible sonnd in any building. By ALEXANDER 

 SAELTZER. 



" A practical and very sound treatise on a subject of great importance to 

 architects, and one to "which there has hitherto been entirly too little attention 

 paid. The author's theory is, that, by bestowing proper care upon the point 

 of Acoustics, the requisite ventilation will be obtained, and vice versa. 

 Brooklyn Union. 



Myer's Manual of Signals. 



New Edition. Enlarged. 



12mo. 48 Plates full Roan. $5.00. 



MANUAL OF SIGNALS, for the Use of Signal Officers in the 

 Field, and for Military and Naval Students, Military Schools, 

 etc. A new edition, enlarged and illustrated. By Brig. -Gen. 

 ALBERT J. MYER, Chief Signal Officer of the Army, Colonel of 

 the Signal Corps during the War of the Rebellion. 



Larrabee's Secret Letter and 

 Telegraph. Code. 



18mo. Cloth. $1.00. 



CIPHER AND SECRET LETTER AND TELEGRAPHIC 

 CODE, with Hogg's Improvements. The most perfect secret 

 Code ever invented or discovered. Impossible to read without 

 the Key. Invaluable for Secret, Military, Naval, and Diplo- 

 matic Service, as well as for Brokers, Bankers, and Merchants. 

 By C. S. LARRABEE, the original inventor of the scheme. 



