230 ADDITIONAL NOTICES. [May 10, 1858. 
plan or of a printed one may be transferred to the zinc, and 50 impressions taken 
off for 50 shillings. 
It was a matter of great importance to find a ready way of reducing drawings 
from a larger scale to a smaller one, and after many experiments photography 
was found to fully supply the requirements of the office. By its means, and 
without sensible distortion, one man is literally able to do the work of 100 
skilled draughtsmen ; thus, a single individual, with the aid of a printer and 
a labourer, produced in 6 days 12 square feet of photographic reductions, 
besides 135 impressions in all from photographic positives that had already 
been prepared. One of these reductions is given to the engraver to work from, 
another to the officer who inserts the contours, and so on, and by this arrange- 
ment everything proceeds pari passu. 
Experiments were made to ascertain the relative powers of the different 
colours for producing photographic tints, and the following scale of colours was 
found to produce a scale of shades from nearly perfect white to jet black : blue , 
purple , red , orange , yellow . All the streets and houses in the plans are 
coloured yellow, and appear as jet black in the reductions. The hill shading 
on the 6-inch maps is similarly done with bold yellow strokes, the artist 
guiding his touch by the fine contour lines or the levels which are engraved 
upon them. When these are reduced to the 1-inch scale, the contour lines, 
&c., become quite invisible, and the hill shading stands out in dark relief. 
Most beautiful specimens are given of these photographic reductions. 
Lastly. When the plates have been engraved it is found expedient never 
to use them for printing, but to keep them as permanent references, and to 
prepare any required number of electrotype duplicates from them. This art 
of electrotyping is here carried on, as Colonel James considers it, to perfection. 
There is no loss of sharpness in the duplicates, additions and alterations can 
be made without tampering with the original plate, and there is no fear of a 
gradual deterioration in future impressions. 
The effect of the vote of the House of Commons, June, 1857, has been to 
cause the discontinuance of the surveys on the large scale, and at present the 
rural districts are being surveyed and drawn on the same 6-inch scale on 
which they are engraved, and afterwards they are reduced by photography 
and engraved on the 1-inch scale.— F. Gr. 
