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An improvement in Irrigation. By Lieut. A. Murray Mcgregor, 66th Regiment Native Infantry.
My principle is, that the greatest power is obtained by keeping the line of draught horizontal, and at the height of the animal's shoulder as is shewn by the mode in which the gigs used in trotting matches are built. This plan was tried at Cawnpoor, by Mr. Stubbs, provisioner, and he assured me, that he drew one-third more water by my method, than lie had upon the old principle; and that the cattle were less distressed than by the old mode, as it is more laborious to walk up an ascent than upon level ground; and he had three more wells prepared upon my principle, as it was by far less expensive, and the ground formerly lost by the inclined plane was saved to the garden, by adapting the hose, (which I do not claim as My invention.) One man will do all the work, and a pair of bullocks will draw the water required in twothirds of the time required formerly; and the expence is much less. The rope passes over the block or wheel A, and under that at B, by which great power is obtained.
By the common plan in use the excavate ground becomes at once t dead loss, and the labour of walking up the inclined plane is very great, as it is required to be very steep. I have therefore, by the dotted line B, shewn how the alteration of the present system can be made. It will be requisite, however, to fill up the slope of the inclined plane to the level of the ground as marked at C, but that can easily be done : it would not cost more than three or four rupees.
N. B.—On the old principle, the driver is obliged to sit on the rope, to keep the yoke on the bullock's necks.
The accompanying are two very compendious Logarithmic Tables, in which I have endeavoured to combine the minimum of size, with the maximum of utility.—By Capt. Shortrede.
The mode of using these Tables is so similar to that of the Tables in common use, that it is almost needless to give any particular directions on the subject.
It is to be understood that every number in the body of each Table is supposed to consist of 5 figures; the single figure on the left in columns 0 and 5 being common to the succeeding columns on the same and following lines. These leading figures increase progressively by unity, and nine changes occur in each Table. To mark this change, when it occurs any where not at the beginning of a line, the numbers subsequent to the change are put a little lower than their usual place, in order to indicate that their first figure is to be supplied from that on the lower line, besides which, the first following zero is printed black to distinguish it as a change figure.
The Table of common Logarithms (neglecting at present those beyond 1000) has in its first column marked Nat. Num. the natural numbers from 10 to 100, and immediately adjoining in the column headed 0 are the corresponding Logarithms, (for numbers between 1 and 10, the Logarithms are opposite the tenfold number): for numbers for three figures the two first being found in the first column, the 3rd is to be found among those at the top, and in the body of the Table is seen the corresponding Logarithm. For numbers of more than 3 figures the Logarithm is found by adding to that in the Table the proportional part for the 4th and subsequent figures, (allowing, if need be, for the difference between the proportional part in that and the next line according to the distance of the 3rd and following figures from the middle of the line.)
Required the Log. of 33952. for 339 the Table gives, . . 53020 for 5 Propl. part gives, .... 65 for 2 Propl. part gives, 2-6
Log. Required, 53087 6
The 3d and subsequent figures of 33952 being about midway between 3345 and 3445, the proportional parts should be the half of those given in lines 33 and 34. Instead of 65, the proportional
Number Reqd. 33952
The Antilogarithmic Table contains the numbers to a series of Logarithms from 0 to 999. The first column contains the two first figures of the Logarithm, the third being found at the top of the columns; and in the body of the Table is found the •corresponding natural number. When the Logarithm consists of more than 3 figures, the proportional part for the 4th and subsequent figures, taken in the same' line, are to be added to the number given in the body of the Table.
(The proportional parts being given for the mean difference at the middle of the line, may be adjusted, if need be, to their proper value, by allowing at sight for the difference between their value in that and the next line, according to the distance of the 3rd and following figures from 45 the middle of the line.]
Required the Number to Log. 71572. For Log. 715 the Table giyes.60954 for 7 Propl. part is .... 98
for 2 Propl. part is .... 2 8
Here the 3rd and subsequent figures being close to the middle of the line need no correction.
Inversely Required the Logarithm to Number 61055. Given Number 61055 Table Number next less .. 60954 The Logarithm is 715
For difference next less 98 Proportional part is 7
For difference next less 2-8 Proportional part is 2
Log. Required, 71572