C. Abbe on the Repsold Portable Circle. 309 
near Quebec, a furnace thirty feet high, which, it is ex 
ia will enable them to treat fifty tons of seven per cent ore in 
| twenty-four hours. 
3 The application of the Water-furnace to the treatment of we 
sulphuretted ores of other metals, presents many points of in- 
terest, whose consideration is reserved for another time. 
Montreal, Feb. 21, 1867. 
| ARrT. XXXIV. —The Repsold obese Vertical Circle; by 
CLEVELAND ABB 
(Continued from page 216.) 
7 As to the methods and formule used in connection with the 
ing computation gives us the approximate north point of the 
azimuth circle and the me angle. 
Put 90°—d=a s—a=e =" 
90°— g—b s— b= 8 
ane s—c=/y cet Or 
sine sin@ siny 
sins 
W=atbpe %w=e+ $+ 
The Gaussian formule give for ths azimuth, parallactic angle 
and hour angle, 
(B.) tant}A=—— , tanjp=—— tanji=—— 
sin @ ee siny 
tangA tan$p tandi— =, 
The computation with its controls is of course performed with 
4-figure logarithms. The observed azimuth, plus or minus the 
mpu ves the north point of the circle. The computed 
, plus the tabular R.A., gives the sidereal time, whence is found 
the clock correction. 
ou, XLII, No, 129.—May, 1867. 
