t-Iaupt..] to [Nov.1 



Field: Plot = — . P and F being always reduced to the same deno- 

 mination. 



Thus a scale of ^5-5 is 5280 ft. of field to 1' of map or one mile to 1 ft. 

 of a mile to V, and not 12" to I mile 



It is evidently incorrect therefore to indicate the scales of maps as so 

 many inches t o a mile as is frequently done. Take the case of the recent 



Geological maps of one of our sister stales said to be plotted on a scale of 

 3" to 1 ■»• or 3" to 63,360" = &£f££ = 21,120 that is to say the map is 

 21,120 times larger than the state itself, a manifest absurdity resulting from 

 considering the map as the first quantity or standard rather than the field 

 itself. 



In such cases errors of interpretation can scarcely arise as the intention 

 is so evident, but there are numerous others that may lead to misconstruc- 

 tion, as where the drawings of small objects are nearly of the same size- as 

 the things represented — thus a scale of J" to 1" would confuse a mechanic 

 unless he happened to know which was the lamer, the object or the drawing. 



So the expression \" to V is likewise incorrect as it is the reciprocal of 

 the ratio intended — the inches evidently referring to the drawing and the 

 foot to the object. As it stands, applying the definition of rations deduced, 

 it will be equal to 12 -=- \ — 48, making the drawing 48 times the size of 

 the model — it should be 1' to \". 



If it be remembered that the antecedent always refers to the given object 

 and the consequent to the drawing, no difficult} - can arise. It will always 

 happen then that if the drawing is on a smaller scale than the thing deline- 

 ated, the ratio will be a proper fraction ; if larger, an improper fraction, 

 and if equal the value will be unity, or \. 



It is hardly necessary to call attention to the fact that the number of 

 scales in use is practically infinite, and that serious inconvenience results 

 therefrom to Engineers and Surveyors whose work extends over several 

 counties or states, making it frequently necessary to re-draw large sections 

 of country. In compiling atlases it is the practice of publishers to vary 

 the scales according to the amount of territory to be represented that the 

 sheet may be filled up, but nothing is gained thereby since the scale used 

 for the greatest area to be represented will show with equal clearness all 

 the features of any other area. Moreover the eye becomes accustomed to 

 estimating distances on the maps, with sufficient accuracy for a reconnais- 

 sance, when the scale is uniform, but when variable it leads to great con- 

 fusion, and especially when the publisher has neglected to indicate the 

 scale, as sometimes happen-. 



It is very desirable to establish, if possible either by recommendations 

 of scientific societies or by general laws, some conventional scales for maps 

 of various sizes. Taking a stat e of medium area as N. Y. or Penna. for the 

 unit, and reducing it to a convenienl size sheet of paper, say 4 X 3 ft., 



would require a scale of ,,, . the same as is used by the U. S. Coast 



Survey for general charts and reconnaisartce, but too small for most other 

 purposes. Larger states could be plotted on the same scale by dissecting 



