PREPARATORY MAPS AND DATA 25 



the rate was from two to four miles per day, with bench-marks 

 established every quarter mile. 



These sheet-maps may be indexed on the large map, num- 

 bering the sheets to correspond with the numbers on the map; 

 or a separate index-map may be drawn on one of the sheets 

 and bound up with the others, in sections if need be. 



It is interesting to note that the directions offered above, 

 which have been developed from the general practice of this 

 country, agree in scales, etc., with the instructions for similar 

 work issued by the Local Government Board of England (see 

 Rawlinson's Suggestions, 1878).* 



PROBLEMS 



7. If 5-foot contours on a certain map drawn to a scale of 300 feet 

 to the inch are f inch apart, what is the surface slope in feet per mile? 

 In per cent? 



8. With two barometers, make a survey of an area of about 25 acres, 

 plotting 2-foot contours. Select a part of the city that has marked 

 differences in elevation and for which the street plan is available. 



10. With chain or tape only, make a survey of a portion of some 

 assigned street (about 600 lineal feet). Record the position of all street- 

 lines, trees, posts, fences, including back lines of lots, houses and barns, 

 with all surfaces indications of underground pipes. Plot to a scale of 40 

 feet to the inch. Compute the cost of the survey in units of acres per 

 day. 



11. Compare the cost of making a survey of the city of , using 



the data of this chapter and checking by the results of Prob. 10. 



12. Compare the cost of digging (no sheeting) test-pits, 3 feet wide 

 by 4 feet long to average depths of 1 2 feet, with the cost of wash-borings 

 as given in this chapter. 



13. With a given city map, estimate the cost of running levels and 

 establishing bench-marks for future work, assuming necessary salaries 

 for different members of the party. 



* See also Municipal Engineering, Vol. XXI p. i6l<, 



