1878.1 "*■" [liaupt. 



them. Foreign countries conducting Geodetic Surveys have adopted such 

 a system. In Prussia, Austria and Switzerland the plane table sheet are 

 plotted on a scale of 35500- In I lal y tlie neld work is plotted on a scale 

 of -ooo-o> and in Sweden n>oW- Tlie older British charts and maps wen- 

 made on a scale of 1 m - to 1" or ^j^, and the later maps of 1 '"• to 6" or 

 rrr.' rm. but these latter, while not being large enough to show parish bound- 

 aries with sufficient accuracy, require about six times the amount of labor 

 in their preparation and are inconvenient. The scale used by Prussia 

 and Switzerland for general maps is T ooW(j> or one fourth, that of the 

 detail sheets obtained from the plane table surveys. 



Populous, cultivated and mineral districts in Great Britain are plotted on 

 a scale of r: ^ — 1 m - to 25.344", partially cultivated and thinly settled dis- 

 tricts, on a scale of 1 m - to 6" = mi**- For the plans of cities of over 4000 

 inhabitants a scale of - 3 -£ or fMo 10.56 feet is used, and for towns and 

 villages j-^ 1 ^ or 1 m - to 5 ft. is general. 



Numerous other instances might be cited showing the great variety of 

 scales in use, but these Avill suffice. It is evident that in Government or 

 State Surveys some systematic connection may readily be established be- 

 tween the several scales used, and it is very desirable that this uniformity 

 of scale be made more general. The scale adopted should be just large 

 enough to show clearly all necessary detail. Anything more than this is 

 a wasteful expenditure of time and money. 



For general maps of States showing intercommunications, a scale of 

 rWo-ffT? w il' be found sufficiently large. 



For maps of counties, in toto, a scale of ^o^ 5 will enable all necessary 

 features to be clearly represented ; this scale applied to Lycoming Co., tlie 

 largest in Penna.. would require a map 6^ >< 4H't. For townships the 

 scale of 2^00 i s quite large enough, and furnishes an admirable size for 

 the projection of Geological data. 



For cities, towns and villages some decimal, sub-multiples of the above 

 scales should be used. 



Cadastral maps of farms, parks or estates may be plotted on scales of 



1 1 _ 1 ptr- 



•2 .T |T» 5 0> 1 0111 cl< - ■ 



In indicating the degrees of slopes or the bater of retaining walls, the 

 natural tangent of the angle which the slope makes with tlie horizon 

 should invariably be used. 



To save time in determining the relative values of some of the most im- 

 portant scales in use, and to aid in introducing the metric system of lengths, I 

 have with the assistance of Messrs. Win. M. Potts and J. W. Van Osten, Jr., 

 prepared the accompanying tables of equivalents. The first, gives the 

 number of Miles, Kilometers, Poles, Chains, Yards, Meters and Feet of 

 territory which are equivalent to one inch of map for any given scale. 

 The second, is the reciprocal of the first, and states the amount of map sur- 

 face which would be covered by any one or more of the above units, for 

 any scale. 



PROC. AMER. PHILOS. SOC. XVIII. 102. G. PRINTED DEC. 26, 1878. 



