On Conjugate Hyperbolas. 
213 
1831.] 
with them. Our fourth reason shall be, its frequent passages into granite or gneiss, 
ancl quartz rock. Our fifth, that it is interstratified with clay-slate ; and lastly, 
that from the great rarity of organic remains in the blue limestone which rests 
upon it, the chances are, that that rock is of an earlier age than lias. These rea- 
sonings I know are inconclusive, hut I can hardly deem them superfluous, for it is 
always best to look at a question under dispute in every possible point of view. 
Let me not be considered as underrating Captain Franklin’s labours. No one can 
appreciate them more highly than I do. And I have only to add my hope, that this 
problem, and many others of interest in the geology ot India, will shortly be ex- 
plained to us, from the liberal patronage of the French Government, and the re- 
searches it has encouraged into the Natural History of the country. 
Note by the Author— That salt exists as deep in the earth as any mineral with 
which we are acquainted, is proved by its frequent, or almost universal oceunenc© 
in lava. For instance, some of the lavas of ./Etna are said to have yielded 9 per 
cent, of common salt, by simple washing. The mineral springs of volcanic countries 
are usually strongly impregnated with it, and in this way it is liable to be deposited 
in all formations. 
The writer in the Gleanings does not mention sulphate of lime as occurring, which 
is constantly present in the rock salt formations of Europe. He says, the salts, are 
muriate, sulphate, and carbonate of Soda. Now if we turn to Mr. Piinseps 
Analysis of the hot springs near Hoseinabad, we find that they contain muriated, 
•ulphated, aud carbonated alkali. Need we then search any further for the reason 
of the saline particles of the soil in the Bhartpur district? Near Hoseinabad the 
process of saline deposition is yet going on. What becomes of these hot springs, when 
they approach the surface, and percolate through the soil ? Do they not partially 
evaporate, and leave behind them part of their saline contents? It would be difficult 
to believe that they did not. But it is not unreasonable to suppose, that the saline 
s °il of the Bhartpur country, owes its origin, like the kankar and ironstone, to 
springs long since dry, and which probably burst forth abundantly, either 
simultaneously with, or immediately after the eruptions, which we learn fiom 
G.iptaia Coulthard’s paper, have taken place in the Saugor districts 
III . — On Conjugate Hyperbolas . - 
To the Editor of Gleanings in Science. 
Sir, 
I am induced to trouble you again on the subject of Conjugate Hyperbolas, and 
shall here consider the case in which the plane of the hyperbola is inclined to the 
plane of the cones. And this again subdivides itself into two other cases, first : that 
' n w hich the plane of the hyperbola is inclined to the base of the one pair of opposite 
c °aes, and perpendicular to the other ; and second, that in which it is inclined to the 
bases of both pairs of opposite cones. It will be sufficient to consider the first of 
these cases; and here my object will be simply to show, that the common mode of 
considering the subject is wrong. I am not as yet able to say how it is to be corrected. 
J * s m °re difficult to represent this case by a diagram than the former, and I must, in 
U f S n ' s Pect, make greater demands upon the reader’s imagination. 
Let ABC, DCE, and BCD, ACE, (Fig. 3.) be two pairs of opposite cones, mutu- 
) conjugate. The planes of the base of these cones are the planes perpendicular to 
, 1C P a Per passing through the lines AB, BD, DE, EA, which are the diameters of the 
^ase of the respective cones. Let T, U, V, W, be the centres, and let these planes 
All tr Pre8ented by AFHB, BQSD, DKME, ENPA, respectively. Then let FGH 
t f > be in one plane, inclined to the bases AFHB and DKME, and perpendicular 
QSD > ENPA, so that the angle GXT should be acute, and LYV obtuse, the 
