42 
MR. C. CHAMBERS OK LUNI-SOLAR VARIATIONS OF 
28. On these curves we first remark that, as at Bombay, the variations of the f c .i(h ) 
and f s .i(h) types are quite subordinate in magnitude to those of the f c . 2 {h) type ; that the 
y,, 3 (//) curve is twice reversed in the course of the year, and that, whilst for December 
and January (fig. 17) it has a greater range than the corresponding winter curve 
(fig. 1) for Bombay, the reverse curve for July to September (fig. 20) has a smaller 
range than the corresponding autumn curve (fig. 4) for Bombay. The relation of the 
f c . 2 (h) curves of the two stations generally is such that the superposition of a constant 
variation of the character of the winter f c .o(h) curve, but of smaller range, upon the 
Bombay curves for each season would convert these into curves having the same prin¬ 
cipal characteristics as those of the same season for Trevandrum; and, in agreement 
with this, the reversal in the first half of the year occurs later at Trevandrum than at 
Bombay, and the reversal in the last half-year occurs earlier than at Bombay. 
And here again we must insist on the reality of the variations now brought to light 
as true physical phenomena, which exhibit themselves not alone at a single point on 
the earth’s surface, but are well marked in the observations of two stations that differ 
by nearly ten degrees in latitude, and the observatories at which were necessarily fur¬ 
nished with independent instruments, and had independent directors. 
Postscript. 
(Added September 23, 1886.) 
The late John Allan Broun, in discussing the Trevandrum observations for the 
ten years 1854 to 1864, came to the conclusion that in the lunar diurnal variations of 
declination in each month of the year the amount of movement is, as in the solar 
diurnal variation, greater during the day than during the night; and the writer of 
this paper has shown in it that in each of four seasons of the year the same holds at 
Bombay with respect both to the declination and horizontal force. Whilst admitting, 
however, that Broun has priority of publication of this fact as regards the declination 
at Trevandrum, the writer avers that he has in no way been guided by Broun’s 
previous investigation, nor was he aware of the existence of Broun’s paper # when 
he made the discovery with respect to the declination at Bombay. Moreover, the 
writer’s line of investigation was that of Sabine, modified by himself, and not that of 
Broun ; and an account of the first results of its employment was read before the 
Royal Society on the 1st February, 1872, a date antecedent to the reading of Broun’s 
paper before the Royal Society of Edinburgh, which did not take place till the 
6th May, 1872. The writer also readily acknowledges that in the paper already 
referred to Broun enunciated some relations of the movements near sunrise in the 
lunar diurnal variations of declination in different months, which relations fit in well 
with the idea of a limi-solar variation when once that idea is conceived; but he finds 
Transactions of the Royal Society of Edinburgh,’ vol. 26, page 735. 
