164 
On Irrigation, and Inland Navigation, 
[Jim, 
tbe cone PCO is b r, and its conjugate axis is b. Hence the transverse axis of 
the hyperbola conjugate to that, is b, and its conjugate axis b r. Now the trans- 
b 
verse axis of the hyperbola cut, by Hutton’s method, from the cone OCN, is — » 
T , 
and its conjugate, (by reasoning in the same manner with the cone OCN, as with 
PCO,) is b. Then b : b r : : : b; that is, the proportion of the transverse 
T 
to the conjugate axis in these two last hyperbolas, is the same; and hence they 
are similar. 
& 
II On Irrigation and Inland Navigation, as applicable to the 
Dek,han; by Captain George Tvvemlow, Artillei'y. 
The numerous reservoirs and irrigating tracts which may be traced all over 
the Dek,han (and which, it is believed, were made chiefly previous to the devastating 
wars carried on by the Brahmans and solar races, against the Budhist and lunar 
tribes), evince that the country had attained a high state of cultivation and 
prosperity ; and it is believed that their revival would renew such. 
The Mahrattas, who lately held the country, were a nation of plunderers, 
who forced the lands into cultivation, by external aids ; each Potail, or head man 
of a village, being a robber, as well as cultivator, who foraged in neighbouring 
countries, foi cash and cattle, to enable him to cultivate the arid tracts, on the 
rocky plains of his retreat, where no precautions were then taken to husband 
the periodical rains, as was usual under former and more settled governments. 
The British received the lands from the Mahrattas ; and since they neither 
admit of the external aids obtained by the cultivators of Mahratta governments, 
nor have put in order the reservoirs and irrigating canals of the Budhist and 
Deo governments, it is probable that the country will not repay its expenses. 
It is believed that, by a due attention to three points, the Dek,han might again 
become (what it once undoubtedly was), a populous and rich country, abounding 
in large cities and marts, 
1st.— Irrigation, by means of weirs or dams, with side channels from the 
rocky falls of all the streams. 
2nd.— Inland transport of surplus produce at a cheap rate, and exempted from 
vexatious transit duties. 
3rd.— Full employment for the present plundering tribes, by causing to be 
expended, on public works, a portion of the cash now dissipated in keeping 
them in subjection, and in outlawry or idleness. 
Remarks on Irrigation. 
The periodical rains fall in the Dek.han chiefly during the months of June, 
u>> August, and September, and then in such abundance, as would be ample 
for the whole year, if the supply were husbanded. 
Again, towards the end of the year, and also in March or April, there are 
generally heavy showers, which seem naturally and beneficially purposed to re- 
plenish the reservoirs and tanks. 
