erp) 
On the Utility of Contour Lines on Plans. By Captain 
VetTcu, Royal Engineers.* With a plate. 
The Commissioners are desirous of being informed by 
you what scale and description of survey you consider, from 
practical experience, to be the most eligible for house and 
street drainage, and sewerage, and for the regulation of new 
buildings, or for other public purposes to which a compre- 
hensive survey would be applicable ?—The best and most 
appropriate scale for the several purposes required, I con- 
sider to be 88 feet to one inch, or one mile to 60 inches. This 
will be adequate to shew the position of the sewers, water- 
pipes, and gas-pipes, and would serve the purposes of valu- 
ation, and of setting out improvements. The valuation map 
of Leeds was constructed upon a scale of 198 feet to an inch, 
but it proved too small for several purposes, and was after- 
wards, at some expense, enlarged to a scale of 99 feet to an 
inch, or double the original size ; but the effect of plotting to 
a smaller scale, and enlarging afterwards, has the effect of 
magnifying any inaccuracies ; whereas if the plan be plotted 
in the first instance toa large scale, and afterwards reduced, 
any little inaccuracy will be diminished, or disappear. The 
Ordnance plans of Dublin and Windsor are on a scale of 88 
feet to one inch, and the advantages of that scale for LARGE 
TOWNS, have become very apparent to me. ‘To the plan of 
the site of the town, I would propose to add the cropping out 
lines of the different strata, as it appears to me important 
to mark the soils which are retentive or absorbent, as clay 
and gravel. I would propose on the plan to trace the water- 
shed lines, and also the contour lines, or lines of equal alti- 
tudes, say at every three or four feet of elevation. 
Will you describe more particularly, for the information of 
non-professional men, the uses of contour lines on surveys ? 
—The ground plan of a town shews the exact dimensions 
and relative distances of spaces, but it gives no knowledge 
_ * Extracted from Captain Vetch’s Evidence, taken before the Parlia- 
mentary Commissioners of Inquiry into the state of Large Towns and 
Populous Districts. 
