Page 663 the "smooth sheet 72 



The types of cellulose acetate ordinarily available are described below. All four 

 kinds can usually be furnished b}^ the Office although only the first three are on the 

 General Schedule of Supplies. 



(a) Cellulose acetate sheeting, special low shrinkage, one side frosted for drafting, 40 inches wide by 0.008 inch thick, in sheets 

 50 and 60 inches long and in rolls. 



(6) Cellulose acetate sheeting, ordinary grade, one side frosted for drafting, in sheets 20 by 50 inches in size, and in thickness 0.005 

 inch, 0.0075 inch, and from 0.01 inch to 0.125 inch. 



(c) Same as (6), except both sides are clear. 



(d) Cellulose acetate sheeting, ordinary grade, clear, available in rolls up to 40 inches wide and from 0.00088 to 0.002 inch thick. 

 Sold under the trade name of "Rigid Kodapak" by Eastman Kodak Company. 



The frosted sheeting is preferable for either pencil or ink work. The clear sheeting 

 cannot be used for pencil work and is not too satisfactory for ink work. 



To ensure ease in drafting and the most permanent bond of the celluloid ink (see 

 7261), the surface of both the frosted and clear sheeting should be cleaned thoroughly 

 with either ammonia (U.S.P.) or magnesium carbonate, applied with a soft cheesecloth. 

 Tracing cloth powder can also be used for this purpose, but magnesium carbonate 

 seems to give better results. 



72. DRAFTING AND LETTERING 

 721. Character of the Drafting 



Artistic drafting and lettering are neither necessary nor desirable on a smooth 

 sheet. A hydrographic survey is an engineering product and the resulting smooth 

 sheet should give the appearance of such, rather than that of a work of art. The final 

 result must be first, accurate; second, legible; and third, neat. Wliile neither expert 

 draftsmanship nor penmanship is required, the drawing should be of such quality that 

 there will be no impression of carelessness, since a drawing apparently carelessly made 

 is likely to reflect on the accuracy and the reliability of the field work. Care and 

 patience combined with sufficient practice will produce the necessary accuracy and 

 legibility. 



It is particularly important that the smallest details appear on the smooth sheet 

 accurately and clearly. In general, it should be possible to read, without difficulty, 

 everything on the smooth sheet without the use of a magnifying glass. Those engaged 

 in constructing, inking, and lettering smooth sheets should constantly keep in mind 

 the fact that photographic copies of smooth sheets are frequently made for the use of 

 agencies and persons, who have no access to the original documents, and that often 

 these copies are at a one-half reduced scale. 



It is only by following prescribed standards that an entirely satisfactory smooth 

 sheet will be produced (see fig. 171). Particularly important is the use of standard 

 symbols (see figs. 169 and 189), as great confusion often results where nonstandard 

 symbols are used or where symbols are drawn so poorly as to make misinterpretation 

 possible. Soundings, in particular, must always be clear and legible (see fig. 163). 



722. Orientation of Smooth Sheet 



North shall always be considered the top of the smooth sheet, whether or not the 

 projection lines are parallel to the edges of the sheet. In plotting and inking smooth 

 sheets all lettering and numerals of any kind shall be so lettered as to be read from the 

 south (see 7733). Where geographic names or legends cannot be lettered on an east- 

 west line, but must be lettered at an angle or on a curve, they shall be so arranged as to 

 be read when looking directly north (see 7872) . 



