276 On different Methods of raising Water for Irrigation, [Sept, 
Draw E W for tlie parallel of the star : lay off S m = x and Mm (perpendicular 
to E W) = y : also Sm' = x\ and Aim! = y , 
Join and produce MM': make Sd, S d r = moon’s semidiameter, and draw dl, 
d’ E perpendicular to E. W. I, shows the time of immersion, and E, that of emer- 
sion. Then, as the increase of the moon’s apparent AR. during the interval be- 
tween the 1st and 2d instants for which the calculations have been made, or as 
mm : l h : : m T : the interval of time between the 1st instant and the immersion; 
and similarly for the time of emersion. In the present case, I found for the appa- 
rent time of immersion 9 h 09 n \ which answered to ll h 01“ by my chronometer: 
I observed it at ll h 03“ ll 8 differing only a little more than two minutes from 
the calculation. 
In order to find the place where the star will reappear from behind the moon; 
On d as centre and radius equal to the moon’s semidiameter describe a circle : make 
the angle E if Z = V, then will tfZ be tlie vertical, which will serve to direct the 
observer to that part of the moon's disc, where the star (SI will reappear. But as it 
will seldom happen that either of the calculations are for the exact time of emer- 
sion, the angle V will require to be estimated, which may always be done with suffi- 
cient accuracy. 
Wilh regard to the signs : the distances x,x f y are laid off to the right or to the 
left of S according as they are positive or negative : y,y\ are laid off above or be- 
low the line E W. according as they are positive or negative : and Z lies to the right 
oi to the left of E, according as V is positive or negative. In strictness when the star 
has any considerable declination, the quantities .r y x ought to be reduced bymulti- 
p!ymg them by the cosine of the Star’s declination; but this is quite unnecessary. 
X. On different Methods of raising Water for Irrigation, 
[To the Editor of the Gleanings in Science. 1 
Sir, j 
h p I nerpn t n a w ti0n T W u h , t , h< i Vl P Art . of > ar 7lh No. should the following memoranda 
ne acceptable, I shall he happy in having communicated them ; in the hope that 
f' lrif '’ limvev<,r trifling, may induce others more conversant with mechanics 
to rodH-cTl 1 ,!" 0 ' 1 " wluch , nti ’"y> faciHty, and cheapness, may all combine 
coun^Ta imll^ 0 desirable results fr0 “ mrigation ; which in many parts of this 
country m indispensably necessary to assist vegetation. 
IatoU , fi ! >lds f rom . tanks, by means of baskets, at different ascending 
simik Mian of the ! “• °T ° f yoUr firSt ftnraber8 - Behar the common and 
. ‘ til 1 r r 18 composed of the forked branch of a tree for the 
fulcrum , a bamboo for the lever ; and a lump of earth for the power. With this 
