788 EXPERIMENT STATION RECORD. [Vol.40 



the longer the mixing continues the better the results will be, but that in 

 recent tests mixing relatively dry mixtures longer than three minutes did not 

 prove beneficial. In addition, the theory of proportioning concrete mixtures is 

 summarized in general and with special reference to draiutile and pipe 

 manufacture. 



Hydra ted lime in road concrete (Concrete [Detroit. Mich.], IS (WIS), No. 4, 

 p. 133, fig. 1). — The results of first tests of the effect of hydrated lime in road 

 concrete indicate that the compressive strength increased directly as the lime 

 content increased from to 7.5 per cent. 



Public Roads (U. S. Dcpt. ,\<ir., Public Roads, 1 (1919). Xo. 9, pp. 61,, figs, 

 .'t). — This issue of this periodical contains 20 short articles bearing directly on 

 highway engineering. 



Land clearing, B. W. Housholder (Michigan Sta. Sjicc. Bui. 90 (1918), pp. 

 28-31, fig. 1). — Data are briefly reported to show that under peninsular condi- 

 tions in Michigan it will cost approximately $25 per acre to Clear cut-over land 

 of hardwood stumps, brush, and slashings, using the blasting method. 



The farm tractor, W. Aitkenhead (Indiana Xta. Circ. 89 (1919), pp. 2k, figs. 

 12). — This circular reports the results of experiences of from 95 to 100 repre- 

 sentative tractor users in the State of Indiana, working farms of from 100 

 to more than 500 acres. 



"The fuel cost per acre is variable, depending on the type of soil and the 

 general efficiency of the tractor and plow. With gasoline as fuel, the highest 

 cost given was $1 per acre for plowing stiff clay 8 to in. deep. The lowest 

 was 50 cts. per acre for sandy clay plowed to a depth between 7 and 8 in.; 

 00 cts. per acre may be taken as the average cost of plowing 7 in. deep under 

 Indiana conditions. The cost per acre, using kerosene as fuel, is considerably 

 lower. The lushest cost given is 50 cts. per acre for plowing clay land with a 

 two-bottom plow, 7 in. deep, and the lowest is 25 cts. per acre for loose bottom 

 land plowed 7 in. deep. The average tractor is using 3 gal. of kerosene per 

 acre, costing about 12.5 cts. per gallon to plow between 7 and 8 in. deep." 



Out of 94 tractor owners, S4 reported a saving of two to four horses, and 10 

 no saving in horses due to the use of the tractor. " The farmers reported, 

 with very few exceptions, that their two or three-plow tractors dispensed with 

 the services of one man and two or three horses. . . . 



"The almost unanimous preference was for a three-plow size: in fact, with 

 two exceptions, every owner of a two-plow tractor purchased before IMS in- 

 timated that if he bought another tractor, it would be a larger one. Pur- 

 chasers of the newer 1918 models of two-plow tractors generally expressed 

 themselves as satisfied." 



Out of 95 tractor owners 77 expressed themselves as being satisfied with the 

 tractor, 11 were uncertain, and 7 were dissatisfied. Out of 95 owners 4S re- 

 ported an increase In acreage due to tractor use. Twenty-seven were plowing 

 6 to 7 in. deep; 40. 7 to 8 in. deep; 17, 8 to 9 in. deep; and 5 over 9 in. 



General information is given on the construction and operation of a tractor, 

 and a trouble chart is appended. 



Hay stackers, II. B. McClure (U. S. Dcpt. Agr.. Farmer*' But. 1009 (1919), 

 pp. 22, figs, IS). — This describes different types of hay stackers and gives prac- 

 tical information regarding their cost and use. 



"Stackers are comparatively inexpensive. The most costly typos, the over 

 shot and the swing-around, may be bought for from $45 to $75. and home- 

 made types may be made for a few dollars. If the poles are cut on the farm. 

 the homemade tripod or derrick stacker need not cost any more than an ordi- 

 nary barn-hay fork without the track. The fork and rope from the barn may 



