1917] RURAL ENGINEERING. 785 



ments in a grove at Orlando showed that heads of 25 gal. per minute were ade- 

 quate for ideal furrow-Irrigation methods." 



Experiments with low-pressure pipe systems are also described and some 

 important points in the design and equipment of an irrigation plant are dis- 

 cussed. 



Investigations in cost and methods of clearing land, M. J. Thompson {Min- 

 nesota Sta. Bill. 163 {1916), pp. 31, figs. 26). — Investigations on the methods and 

 cost of clearing 15 acres of cut-over timberland at the Northeast Demonstra- 

 tion Farm and Experiment Station are reported. 



The land averaged more than 200 stumps to the acre, these having a diameter 

 of about 12 in. at the base and 10 in. at the cut-off. Sixty per cent of the 

 timber was green. The soil is a somewhat stony clay loam with a clay subsoil, 

 generally reddish, but in some places bluish gray. The timber was about 57 

 per cent balsam, 16 per cent birch, 13 per cent pine, 6 per cent cedar, 3 per 

 cent tamarack, 1 per cent spruce, 1 per cent balm of Gilead, and 3 per cent 

 miscellaneous. The lower grades of dynamite were used on all kinds of stumps 

 except green birch, for which 60 per cent was found most efficient. The land 

 was divided into three tracts of 5 acres each. On tract 1 the clearing was 

 forced with dynamite. On tract 2 the stumps were first split with small charges 

 of dynamite and then pulled with a machine. Tract 3, after being brushed 

 out, was seeded to clover and timothy for pasturage, and clearing with dyna- 

 mite was postponed 5 years, until 1918. The following conclusions from prog- 

 ress results were drawn : 



" Cost and method are determined largely by the character of the soil and 

 the kind of vegetation. The returns in forest products, cordwood, pole wood, 

 fence posts, and saw logs cover the cost of brushing and other clearing work 

 up to the stumping stage. The cost per stump for blasting and pulling on 

 tract 2 was almost identical with the cost of explosives alone on tract 1. The 

 cost of clearing was much less on tract 1, since much less labor was required 

 in piling and burning the stumps. 



" The cost per stump for removal was least for the man-power machine, 

 slightly greater for the horse-power machine, and greatest for dynamite (this 

 was for green timber and did not include the cost of piling, which makes the 

 use of dynamite the cheapest method by a good margin). . Some relation may 

 apparently be established between the size of the stump and the size of the 

 charge required to remove it. 



" The man-power puller has a limited field where the conditions correspond 

 to those at the Northeast Station. It works to best advantage on the small 

 new farm where the farmer has very limited means. ... It is evident 

 that under conditions existing on the average farm in the region of the station 

 dynamite is usually to be preferred to the stump puller, either alone or in 

 combination. 



" The plan of clearing being followed on tract 3 will not only be carried out 

 at a lower cost but is actually giving a larger net return in pasturage the first 

 year than has been realized from the first crops from land on which the clearing 

 has been forced. . . . 



" Following the removal of stumps from cut-over timberlands, on account 

 of the shallow covering of vegetable matter, care should be taken to plow 

 shallow the first time and to take immediate steps to increase the humus by 

 seeding the land to clover and grasses, using barley or oats for a nurse crop." 



Public road mileage and revenues in the Southern States, 1914 {XJ. 8. 

 Dept. Agr. Bui. 387 {1917), pp. 52+LXXI, fig. i).— This bulletin is a compila- 

 tion which shows mileage of improved and unimproved roads, sources and 

 amounts of road revenues, and bonds issued and outstanding, and presents a 



