MATHEMATICAL SECTION. ae 
The epoch for both systems of elements is 1873, July, 17.0, 
Berlin mean time. 
The ecliptic and mean equinox are for 1873.0. 
The resulting secular variations in one Julian year are the fol- 
lowing: 
Secular variation of the eccentricity, or de== + 1.268; 
. “ ~~ inelination, or oi=— 1.649; 
3 “ ascending node, or 62 = — 61.031; 
is “ ~~ longitude of the perihelion, or dz = + 59.116; 
> “ mean longitude, or 6D = — 83.429; 
The paper was discussed by Messrs. PAuL, H1Lu, and Woop- 
WARD. 
2ist MEETING. May 27, 1885. 
The meeting was called to order at 8:15 by the Chairman, Mr. 
G. W. Hitt. 
Seventeen members present. 
At the request of the Chair Mr. Wintock acted as secretary pro 
tem., Mr. BAKER being absent. 
Mr. R. 8. Woopwarp read a paper on 
SOME PRACTICAL FEATURES OF A FIELD TIME DETERMINATION 
WITH A MERIDIAN TRANSIT. 
[ Abstract. ] 
An important desideratum in all kinds of field work is the 
adoption of those methods which will secure the accuracy essential 
in the results sought with the minimum amount of computation. 
It is in general easier and more conducive to precision to eliminate 
unnecessary factors involved with the quantity sought than to 
determine their values and allow for them by computation. Very 
frequently also a systematic arrangement of observations will secure 
the maximum precision with the minimum of computation. 
In a field time determination for telegraphic longitude’ the essen- 
tial quantity is the error of the time-piece used at some determinate 
epoch, and the unessential factors are the azimuth and collimation 
of the transit and the rate of the time-piece. It is evident that a 
