WATER CONSERVATION SURVEYS OF N.8.W. LXXXV. 
Department denoted unmistakeably the immense possibilities of 
the western division of the Colony, and it was only by such com- 
prehensive surveys that properly thought out schemes could be 
devised for improving this portion of our estate. 
Mr. Haycrorr said there was very little in Mr. McKinney’s 
paper which admitted of discussion, the information contained in 
it was of such a general character. Nothing for instance had been _ 
said as to the class of instruments used, nor, as Mr. Halligan had 
pointed out, the number of bench matke and distances between 
them. There were certainly errors in the closes, whether made 
by the surveyors of the Water Conservation Department or in 
existence before the work was taken in hand. As regards the 
hard and fast rule laid down of one foot in 100 miles, as the closing 
error, that is not the custom in all parts of the world. The recog- 
nised rule in countries where precise levelling is carried on, is 
that the limit of discrepancy in feet (error of closure) shall not 
Gk0eed 0-012 + distance in imiles ; this variation is in accordance 
With the law of probabilities. Many instances of accurate level- 
ling in America could be cited. Ina length of 4,000 miles reach- 
ing from New York to Chicago and other cities, the closing error 
was only one foot, and the cost varied from £3 12s. to £4 4s, per 
mile. In the levelling carried out in St. Louis a circuit of 240 
miles closed with an error of only 0°001 foot per mile. 
The German practice is very exacting, they do not allow actually 
in a mile; -7” they consider good work, 1-18 inch passable 
Work. It must be understood that this rule is only applicable to : 
short courses : in long courses such as mentioned in the paper the 
tule would be error of closure in feet should not exceed -012 
multiplied by the square root of the course in miles. Thus in 
ase 5, mentioned in Mr. McKinney’s paper, where the error of 
closure is given as 5-07 feet in 1,597 miles, good Continental or 
American practice would only permit of 0°48 feet. As regards 
r McKinney’s reference to errors made in the western parts of 
America, he thought that the rest of the world had a good deal 
to learn from American practice in these matters ; and it must 
