416 Serentitic Intelligence. 
ble only if his tube were » wide, or . pitch w high. If this 
is not the case there is a diminution of the v velocity by friction 
and by conduction of bent: which duadnution is to be calculated 
according to Kirchhoff* by the equation 
: Se Uy 
 apa/ mn 
where w means the velocity in free air, a the velocity in the tube, 
n the pitch - tune, 27 the diameter ie the tube, and y a con- 
stant. This equation I have verifiedt by experiments and have 
determined the poor y to be for glass tubes 
y=0-0235— 
On a later eet this number was again confirm 
Ww ee what numbers would have been shtaiied by Mr. 
Ihlseng with, the second method, had he kept in view this equa- 
tion. He indicates the diameter to be 27=0°019/7; the pitch m can 
be calculated nearly by his Table IV. I find by it numbers lying 
between 1000 and 2000; taking as average 1500 vibrations, we 
find 
u—a=6m and a=326'5m, 
Mr. Ihlseng having, therefore, calculated the velocity of wood 
5 
by means of the dust figures by v= ee the right equation — 
would have been »=326°5~. 
It follows, that for the mean velocity of 4000-——— in wood, the 
number calculated by Kundt’s method is too great aves 7390, The 
gitudinally, but at the same time transversely, and therefore the 
number . vibrations can be determined only very inexactly by 
the curv 
Berlin eae Institut., March, 1882. 
16. The pyre of Cooking and € nase dt a Manual for 
Housekeepers ; NH. Ricuarps. 90 pp. 12mo. Boston, 
1882 (Estes and y ress ).—The practical apteations of chemical 
Ones to some of the ‘amiline processes of every-day household 
ife have never been better presented than in this little book b 
Mrs. Richards. Clear and concise in style, and happy in its illus- 
* Kirchhoff, Pogg. gp ‘geal fos LT. + Kayser, Wied. Ann., ii, p, 218. 
¢ Kayser, Wied. Ann., viii, p. 444 
