42 HYDROGRAPHICAL SURVEYING [chap. i. 



If it is intended to do most of the detail plotting in the 

 field and boats, there should be about three or four boards to 

 every assistant in the survey. 



WEIGHTS. 



The weights supplied by the Stationery Office are of iron, 

 flat, oblong, and covered with leather. 



Drum-shaped leaden weights to supplement these, covered 

 Avith duck or baize, will be found very handy. These can be 

 of various sizes and weights, to suit all requirements. 

 Cylinders 2| inches in diameter and li inches in height are an 

 average size, and can be cast on board in a wooden mould. 



A few others heavier are useful, and some flat weights, 

 2i inches in diameter, and | inch thick, are good for 

 keeping down small tracings. 



TRANSFER PAPER. 



This must be made, not bought, as the stuff sold by stationers 

 always has some oily material in it. 



On to a damp sheet of tracing-paper scrape finely some 

 blacklead, and rub it well in A\dth the hand, a little at a time, 

 allowing it to dry between each application. Rub off the 

 loose particles before rubbing in more. The blacklead is only 

 to be applied on one side of the tracing-paper. It must be 

 done as evenly as possible, so as to ensure uniformity in 

 the tint, but this is assisted by a good rub with a soft cloth 

 when the sheet is finished. Two or' three applications will be 

 sufficient. 



A lump of blacklead for this purpose is supplied to all survey- 

 ing vessels, but the lead from a soft pencil will answer as well. 



It is a dirty process to the operator, but in a few hours 

 enough can be made to satisfy the requirements of the survey 

 for a long time. 



MOUNTING PAPER. 



The consideration of what to plot the intending chart on 

 must be undergone before commencing work. Two methods 

 are in use. 



