Quantity of Water Consumed in Irrigation. 43 



quickly, since errors would be detected at once, and unusual 

 results would lead to further inquiry. 



33. The author's experiments on absorption before alluded 

 to (see par. 19) were conducted as follows : — Several beds, 

 formed by little ridges of clay, and measuring inside 4*8 

 feet square, were kept supplied with water ; five gallons were 

 poured on at a time, each gallon over the area enclosed giv- 

 ing a depth of one-twelfth inch. The object was to ascertain 

 how long it would take for the soil to absorb given quanti- 

 ties of water. A somewhat similar arrangement might be 

 adopted to ascertain the absorbing powers of any soil ; but 

 a measurable depth of water should be maintained, say not 

 less than one inch ; in the author's experiments this was not 

 done. It would be well to note the quantities poured on in 

 given periods, in order that it might be seen when, the 

 absorption having assumed its normal rate, the experiment 

 might be discontinued. At first, absorption would be very 

 rapid, but it would soon decrease. Evaporation during the 

 day, especially in hot weather, would be found to affect the 

 result. In these experiments the following points should be 

 noted : — Nature of soil, nature and depth of subsoil, and 

 the general formation of the substratum in the neighbour- 

 hood, with any other points affecting the escape or retention 

 of subsoil water ; a natural drainage channel or other 

 depression in the ground close by would be likely to assist 

 very materially the escape of subsoil water. The results of 

 these observations would, as a rule, apply only to the case of 

 a canal, and not to a site likely to be selected as suitable for 

 a tank (see pars. 24 and 29). 



33. In conclusion, the author will offer a few remarks on 

 the importance of the results brought to notice in this paper 

 with reference to contemplated irrigation works in Aus- 

 tralia. A canal may of course be constructed, and water 

 supplied for irrigation, notwithstanding very erroneous 

 notions as to the quantity of water required for various 

 crops, the area likely to be irrigated, and on other similar 

 points ; but as all such works partake more or less of a com- 

 mercial nature — a fair return for the outlay being in some 

 form or other expected — it is important that a trustworthy 

 estimate should be formed, or disappointment is likely to 

 result. It is very unpleasant to find, after constructing 

 a long canal, that water will not reach the end of it, that 

 the supply is sufficient for only one-half or one-third of the 

 area it was hoped to irrigate, and that in consequence of 



