OP THE PLUMB-LINE IN INDIA. 709 
by the fluid theory, may nevertheless vary sufliciently to disturb the position of the 
plumb-lme most materiaUy. The space I have selected as the basis of my calculation 
IS no doubt extensive ; but I hardiy think too extensive. I have seen the same kind of 
rock (gneiss) prevail for hundreds of miles in the Himmalaya Mountains ; and can see no 
reason why a space as iarge as I have chosen, 200 miies square parallel to the surface 
and 100 miles deep, may not exist beneath the surface, having a density, too, differing 
much more than T^jth part from the proper density of its locality. 
§ 7. Appekbix, containing a reoiae of some farts of my former Paper. 
21. The results of this Paper may appear in some respects to render the calculations 
of my former communication now unnecessary, as it is here shown that it is not 
improbable that a compensating cause exists sufBcient to counteract the effect of the 
Mountain Mass, at any rate to a considerable degree. But it must be observed that 
the demonstration of the suiflciency of this cause, should it exist in nature, rests 
a togethei upon the process of dissection of the mass and the calculations consequent 
thereon, given at large in that Paper. The conclusions also in the present communi- 
cation regarding the effect of wide-spread, though minute, defect or excess of density 
e ow, rest upon those former calculations. I have thought it well, therefore, to take 
is opportumty of reiising some parts into which errors have crept, as intimated in the 
-^ote to par. 1. 
22. The corrections of the Deflections in meridian, produced by the Mountain Mass 
as 1 exists on the surface, at the three principal stations, have already been given. 
ey are but trifling. I have, since completing this new calculation, gone over the 
ormer one and detected the several minute errors, so as to account for every figure of 
isciepanc} *. This is highly satisfactory, especially when the troublesomeness of the 
calculation is considered. 
The errors have crept m among the calculations at the foot of the Six Tables of my former Paper 
— .x-ivc/xwc KJi. iiij lurmer raper 
(pp. 78-88) . The detafla are as foUowa. The values of H sin ^ /3 cos As, as there given, and the neces- 
sary corrections, are as below 
For Station A. (miles) 
Errors . 
Lune I. 
0772 
Lune II. 
3-656 
+ 0-001 
Lune III. 
4-262 
-0-001 
Lune IV. 
2-602 
Lune V. 
0-095 
Totals. 
Errors . . 
3009 
+ 0078 
3-933 
+0-001 
3-395 
2-493 
+0-001 
0-235 
+ 0-027 
For Station B. 
0015 
1-600 
-0-046 
1-211 
-0-001 
24-559 miles. 
Errors . . 
Errors . . 
0-677 
+ 0001 
2-536 
2-643 
+ 0-020 
1-813 
+ 0-001 
0011 
+ 0-094 
For Station C. 
1-173 
-0-124 
10-575 miles. 
Errors . . 
1-973 
2-103 
0-816 
Errors.. 
+ 0019 
These three final quantities are precisely the same as at the foot of the Table in page 753 
AIDCCCLIX. c 
•5'960 miles. 
