MATHEMATICAL SECTION. 101 
TX =f, OTX = F, OT = J, STZ = 90° — (H+ u) 
TY =g, OTY= G, OY = 4, TZO = 180° — k 
TZ = h, OTZ = H, OZ = 90° — 6, TZS = 180° — (p — &) 
NS = u, NOZ = a — N, TOZ= 90°+(a — N), SZO = 360° — p 
TOX = TOY + 90 = 180° — (4 — N) 
WN is the pole of OT, .. NOT = NTO = 90° 
In response to a question, Mr. Hauy said that in computations 
of orbits of double stars, as little reliance should be placed upon 
measures of distance as possible. Variations of angular velocity 
are far safer. 
Mr. G. W. Hit made a communication on 
A FORMULA FOR THE LENGTH OF A SECONDS-PENDULUM, 
which is published in full tn the Astronomical Papers of the 
American Ephemeris, Vol. III, Part 2, Chapter V. 
138tH MEETING. Marcu 26, 1884. 
The Chairman presided. 
Fourteen members present. 
Mr. Atex. §. CHRISTIE made a communication on 
A FORM OF THE MULTINOMIAL THEOREM. 
This communication is reserved by the author. Remarks were 
made by Mr. Hitt. 
Mr. R. 8. WoopwarpD gave a 
DISCUSSION OF A CONCRETE PROBLEM IN HYDROSTATICS 
PROPOSED BY MR. G. K. GILBERT. 
Remarks on this communication were made by Mr. G1LBert. 
Mr. C. H. KumME LL gave the first part of a communication on 
THE QUADRIC TRANSFORMATION OF ELLIPTIC INTEGRALS, 
which was unfinished when the hour of adjournment arrived. 
