The Work of the Geological Survey. 
155 
When, finally checked and approved, the original coloured copy 
is sent to the colourists, who colour all the maps by hand, the work 
being done by women. Experiments were tried some years ago as 
to the feasibility of producing the Geological Survey maps by colour- 
printing. But with our system of engraving it was found impossible 
at the Ordnance Survey Office to ensure sufficiently accurate registra- 
tion, and there was the further practical difficulty that so large an 
impression of each sheet would require to be printed off that a large 
stock would remain on hand, and new editions and alterations of 
the maps would be impracticable for many years. The original 
system has therefore been retained. It has this great advantage, 
that, by keeping the supply of copies of each sheet just sufficient 
to meet the demand of the public, we are enabled to make any 
alteration of a map which from time to time may be found to be 
necessary without the loss involved in cancelling a large stock of 
copies. 
Some idea may be formed of the nature of the colouring work of 
the Survey maps from the fact that upwards of 180 different tints 
and combinations are employed to denote the various kinds of rocks 
separately discriminated on the maps. It is difficult to find colours 
distinct from each other, yet harmonious, and that will not fade on 
exposure. To guard as far as possible against the risk of fading, 
every colour is also distinguished by its own symbol, which is legibly 
engraved where the colour occurs on the map. 
Two editions of the maps of England and Wales are now issued 
for those districts of which the Drift survey has been completed. 
One of these editions shows all the superficial deposits, and only so 
much of the underlying formations as lies bare at the surface. The 
other edition presents the underlying formations as these would 
appear if the superficial accumulations could be stripped off. Each 
of these editions has its value for special purposes. In all questions 
of sanitation, water-supply, agriculture, and building, it is obviously 
the Drift edition that should be consulted ; while, on the other hand, 
where the information desired has reference to what lies deeper 
beneath the surface, as in the sinking of deep wells and mines, it is 
the “ solid ” edition that will be most usually consulted. The 
difference between the two is merely one of colouring, for they are 
printed from the same copperplate, and as far as the engraving goes 
are exact duplicates. 
The prices of the maps are regulated by Her Majesty’s Stationery 
Office, and are fixed according to the amount of colouring work upon 
them. In England and Wales, full sheets usually range from 3s. to 
8s. 6 d , and quarter sheets from Is. Gd. to 3s. In Scotland and 
Ireland the sizes of the maps are different, but the prices are 
calculated on the same scale, being in Scotland from 4s. to 6s., and 
in Ireland (where the sheets are similar in size to the English 
quarter sheets) from Is. Gd. to 3s. In some cases the price at which 
a map is sold is less than the cost of colouring, but it is estimated that 
the excess of selling price beyond that of cost in other cases will 
compensate for this loss. 
