220 Note on the Ham-Nail in the Mahanuddy Basin. [No. 3, 
2nd. The probability of the average annual rainfall in the Maha- 
nuddy Basin above the Delta, having in 1856 been 90 inches. 
It would be extremely satisfactory in this place to be able to 
point to a register of rainfall for the year 1856, kept at Sumbulpore, 
as furnishing observed facts which might be substituted for the above 
probabilities : but in the absence of the former, I must endeavour to 
measure the latter. 
The probability of the nine inches of rainfall may be rated very 
high I think, for, on the 9th September, 1856, a fall of nine and a 
half inches was observed at Pooree by Dr. Pringle, the Civil Surgeon 
of that place ; to say nothing of heavier rainfalls having been often- 
times observed in other districts similarly situated. 
Again, the rainfall during 1856 having been observed in places 
in the Delta, Pooree and Cuttack, to have been respectively 63J and 
67-i- inches, I conceive that its having been as much as 90 inches on 
the average, in the tract above the Delta, is not at all improbable ; 
indeed highly the reverse. 
Moreover, supposing that I have estimated too highly the annual 
rainfall above the Delta, (at 90 inches) I am inclined to think 
that the error would be found to lie, not in my calculation in No. 2 
but in a possible under-statement of one of the factors ; viz. : the ratio 
of the “ amount discharged by the River” to the whole “ rainfall of 
the tract for though that ratio may in ordinary cases be fairly re- 
presented by f-ths, yet in a rocky basin like that of the Mahanuddy, 
a larger proportion may possibly find its way into the channel of out- 
let, and if this be assumed, the amount presented as the solution of 
Question No. 2 will necessarily be proportionally diminished. 
The general accuracy of the calculations based on “sectional 
area,” “ slope of bed,” &c., &c., formerly submitted by me, having 
been confirmed in a most remarkable manner by evidence altogether 
independent of these calculations (vide Report Part III. Cuttack 
Rivers’ Survey, page 23), and again being further, as I consider them 
to be, corroborated by those based on “ area of basin” and “rainfall,” 
which are given above, I think the subjoined general deductions from 
all the various calculations made, may be regarded as the great facts 
of the Mahanuddy which call for recognition when any scheme, with 
which that river is at all connected, may fall under consideration. 
Is/. The area of the Mahanuddy basin is about 59,000 square miles- 
