498 A. M. Mayer on a method of measuring the 
820° C. the air in the furnace tube will have ia ae to 4 
times its volume at 0° C., and therefore 
333 1- ate 0a xe20) 
A= it will contain 3 the number of wave- 
lengths it aid ‘eitien at O° C., and the length of one of these 
waves in the tube will be 1:3 meter. 
We will now determine the limit of accuracy of the method 
by elevating the temperature of the furnace 100°, or to 920° C. 
At this temperature the velocity of the si po in the furnace 
tube will equal 696 sf peter, and the length of the wave at 
this velocity will be 1°36. But 1™-36—1"-3=0"-06, the differ- 
ence in wave- length pees by the increase in temperature 
from 820° to 920°, and sufficient to cause the serrations to be 
displaced ‘46 of the distance separating the centers of two con- 
tiguous serrations of the organ pipe flame. But by means of 
the manometric flame micrometer ;';th of this displacement can 
be measured, therefore, we can measure an increase of 10° 
Gm temperature above 820°. 
Fro examination of the well established formula for the 
« Siternination of the velocity of sound, it will be seen that the 
: @ecuracy of our determinations of furnace temperatures will 
: glone depend on the precision of the coefficient 00367, which 
_ is the number arrived at by Regnault and Magnus for the 
« &xpansion of air acter a constant pressure; and this is one of 
e will now examine os relation edie between tempera- 
tures and wave-lengths. I have computed two tables; the first 
- gives the velocities of sound and the wave- engi ol the note 
ER, corresponding to temperatures between 0° ©. and 2, 000° 
.; the second those corresponding to temperatures between 
0% C. and —272°48° C. 
; Memperature. Velocity. | Wave-length. || Temperature. Velocity. pepsin 
0° C. “ ] 1 
333m 650 500 849°35 65 
00 389°34 760 1600 872-96 1°705 
200 8°53 “856 1700 895°97 1-748 
300 a7 "942 1800 918-41 i 
, 400 523°14 1-021 1900 940°26 pe 
. 500 560°7 ‘095 2000 9610 je 
. 600 596°03 164 Oe “650 
ft 100 4 "228 — 50 | 300-86 587 
<9 008 at “349 —150 93°14 43 
"1100 747-38 1°458 : 186 
te wn —250 95°60 
_ 1200 T1419 1-512 ea reds 
_ 4300 799-96 aie 
_ 1400 82494 611 
