Travers.—Thomson’s System of Survey from a Legal Point of View, 989 
lation becomes a matter of necessity, from whieh minor points may become 
fixed as opportunities present themselves, in order to obtain an accurate 
system of rectangular co-ordinate distances for the traversed points. Ihave . 
| already shortly alluded to the question of the relative cost of a major tri- 
angulation and meridian circuit minor triangulation systems: which, on 
reference to Mr. Thomson’s figures, I find is stated as eight to one in 
favour of the latter. But it may fairly be asked, even if this were established, 
whether—inasmuch as the cost of the survey of lands into one hundred acre 
sections or thereabouts in this Colony varies, as I am told, from 1s. to 8s. 
per acre before the Crown Grant can safely be issued—the fraction of a 
penny per acre more or less, which would be spent in securing efficient 
checks, would materially affect the total cost? Or whether the practice of 
such economy would possibly compensate for the obvious advantages to be 
derived from securing the superior check system ? 
However, in a return furnished to the Conference of Chief Surveyors, 
in 1878, shewing the total cost of the triangulations executed in the several 
Provinces of New Zealand up to that date, I find it stated that 6,739,920 
acres cost £40,618 to triangulate in Otago; whereas, in Wellington, 
2,496,000 aeres, of major and minor triangulations combined, eost only 
£9,800: thus shewing the relative cost to be two to one in favour of 
Wellington. I give these figures, as furnished in thereturn, merely as matter 
of information, and with no desire to disparage, in this aspect of the 
question, the system pursued in either Province. 
t might, moreover, be asked whether astronomieally determined 
latitudes, at intervals of 60 miles, with portable instruments, furnish a 
sufficient check on the accuracy or otherwise of triangulation. I have 
made inquiries on this point, and am informed that even the most skilful 
observers with such instruments will scarcely venture to assert that a 
latitude could be determined within a probable error of two seconds of are, 
or nearly 200 feet of linear measurement ; and as this error may take either 
a positive or negative direction, it may be concluded that, under the most 
favourable circumstances, there would be a possible error of 400 feet in a 
distance of 60 miles, or nearly seven feet per mile. A reliable check could 
only be expected by this method under similar conditions when the two 
stations are at very large distances apart, for the probable error would not 
thereby be increased, whilst the error per mile would be reduced in pro- 
portion to the greater distance of the stations; so that, for the reasons 
above given, this method could only be relied upon for checking triangu- 
lated distances when the stations are very far apart. Electric differences of 
longitude, measured with the portable transit instrument, are asserted by 
competent authorities to be liable to an error of one second of time, or 
equivalent to 1,150 feet in this latitude. Ll 
