LXXXVI. DISCUSSION. 
be borne in mind that in one sense the making of mistakes was 
the initial stage of experiment ; no doubt the errors referred to 
had been made by land owners and agents. The Yankees were 
cute enough to see the benefits of irrigation, and at the present 
time he believed there was more irrigated land in the United 
States than there would be in Australia at the close of one 
‘hundred years. It would appear from Mr. McKinney’s paper 
that no summit levels are fixed, and it is imposible to say from 
the paper how the levels referred to can be utilised for water 
conservation. 
Mr. Davis said that on the paper as a whole he had not much 
to say, but as regards the question of datum, Mr. McKinney said 
the datum adopted was taken from the Railway Department, #.¢., 
Sydney high water mark. From his experience in levelling he 
had found that the Sewerage Department datum did not corres- 
pond with that of the Railway Department, and again the Rail-" 
way Department did not agree with the Survey Department. 
The want of uniformity was a great hindrance in all classes of 
engineering work, and it would be a good thing accomplished if 
the different departments could agree upon a common starting 
point in this matter. 
Mr. J. B. Henson said that it would be interesting to know 
whether, from the numerous surveys which had been made, 
sufficient information was obtainable to enable a rough contour 
map of the western slopes of the Colony to be prepared. A 
general contour map of a locality was indispensable in the designing 
of sewerage and drainage works, and the usefulness of a contour 
map of the Colony not only in relation to the designing of water 
conservation and irrigation schemes but for other purposes, W4S 
unquestionable. Money expended in the production of such 4 
map would be wisely applied, and if a scheme for contouring the 
whole Colony had not yet been projected the time had arrived for 
taking action in this matter, and a procedure might be arranged 
for embracing the future surveying and levelling done by each 
branch of the public service, . 
