New Mineralogical Hammer. 715 
sec. and the last acquired velocity being double of the mean 
velocity is, in this case, 8 feet per second. But the spa- 
ces described are always as the squares of the last acquired 
inch. sqr. of v inch. sq, of vel, 
velocities. Hence,12 : 8 X8=64 :: 51 : 928, 
ence 1/28=5.29 feet per second, or upwards of 31 miles 
per hour, is the velocity acquired in falling 51 inches, in- 
stead of 1} feet per second, and 1; miles per hour, as es- 
timated by your correspondent. J, 
June, 1823. 
4. New Mineralogical Hammer, by Rev. E. Hitchcock, A.M. 
“T have lately constructed a geological hammer* on such 
a plan as toembrace three or four of those used in Europe, 
both for convenience and economy. Fig. 1 is a side view 
of the hammer. The lower part @ of the head a 4, is a 
little rounded to endure a heavier blow. Yet this curva- 
ture ought not to be very great, as a flat surface is often ad- 
Vantageous. The upper part 6, of the head, is brought to 
an edge: the direction of the edge coinciding with that of 
the handle, as shown in Fig. 2. In the handle, a hole six 
or eight inches deep, and half or three quarters of an inch 
in diameter, is made to receive a steel drill, e f. This, 
when not wanted, is confined in the handle by a spring d, 
closing down so as to cover the hole ate. The hammer 
Without the handle, weighs about two pounds. The handle 
should be made rather larger than is common, as itis liable 
‘0 split when heavy blows are struck while the drill is in- 
Serted in it. 
: rounded face of the hammer a is used in breaking 
specimens from the obtusely angular surfaces of rocks ; the 
edge 6 serves to cleave schistose or laminated specimens, 
and to break common specimens in the cabinet, and the 
drill is often wanted to assist in disengaging petrifactions or 
- > 
minerals deeply imbedded in their matrix. 
: 5. Navigation of Rapids. 
Mr. Edward Clark has recently published in Philadel- 
ia, a “Description of a plan for navigating the rapids in 
* See Plate 5. 
