972 Transactions of the American Institute. 



states that at Chari Pungo lie measured a rainfall of 60 inclies, but 

 this was ill a southeast monsoon. 



Mr. Alanson Xash remarked that the vallej of the Amazon gives 

 the largest rainfall of any place; whatever abstracts the moisture of 

 the atmosphere will bring the rain down. There is no part of the 

 globe that contains as much water as that section ; this is owing to 

 the proximity of the Chimborazo mountains. 



Mr. Emery read a letter of Captain Dent, on the current of the 

 gulf stream. 



Adjourned. 



February 17. 1870. 



Prof. Samuel D. Tillman in the chair ; C. E. Emery, Esq., Secretary. 



Parallel Euler. 

 Mr. Dudley Blanchard exliibited a parallel ruler made b}^ him. It 

 was intended for the use of draftsmen, and which would facilitate the 

 cross-hatching required in making sectional views. Two parallel 

 bars, intended to be placed in proper position upon the paper, are 

 provided, one with a finger-lever and spring-pawl, the other with a 

 ratchet on its upper surface, and with a hinged horizontal arm, 

 adjustable at any angle to its bar. By working the lever on one bar, 

 the pawl connected therewith is caused to act upon the ratchet of 

 the other, and thereby advance the same, together with its angular 

 arm or rule, to the distance required to form the spa(|k between the 

 oblique lines of the cross-hatching, such distance being of course pro- 

 portioned to the exterit to which the finger-lever and its pawl is 

 depressed. It is well adapted for ruling parallel lines of greater or 

 less degree of fineness. 



Deep Sea Sounder. 

 Prof. J. A. Whitney explained Mr. James Bogardus' Deep Sea 

 Sounder, which was exhibited. It consists of a flat frame-work, the 

 lateral portions of which constitute wings to prevent the instrument 

 from turning bodily during its descent. Within this is a vertical 

 spiral vane connected by clock-work at the top with an index finger, 

 •which, in connection with a suitable dial-plate, records the number 

 of revolutions of the vane during the descent, and consequently the 

 depth. Tlie instrument is caused to sink by a weight at its lower 



