86 EXPEEIMENT STATION RECORD. [Vol.38 



later becoming water-logged and sinking through the slot into the sludge 

 chamber. 



" It is too soon to state with conviction the amount of digested sludge that may 

 be expected from small-scale tanks, but one tank indicates an apparent accumu- 

 lation of 2.6 cu. ft. per year per person, and another tank, 4 cu. ft. 



" The only time when tanks required daily attention was during the foaming 

 period, which lasted about 10 days, and during which time some of the foam had 

 to be removed and buried. At all other times attention once a month at most 

 was ample. Since the foaming period has been passed the scum formation has 

 been slight. 



"The decomposed sludge obtained from the small-scale Imhoff tanks re- 

 sembled that obtained in large tanks except that it had a higher moisture con- 

 tent. This may perhaps be explained by the shallowness of the sludge layer. 

 A 15-in. sand bed dosed with settled sewage at a net rate of 190,000 gal. per 

 acre per day during the second summer reduced the average oxygen demand 

 from 63 to 12 parts per million (24-hour at 20°). This is probably ample puri- 

 fication for many cases, but insufficient for others. 



" The sand bed required little attention during the summer months, but what 

 would seem to be a prohibitive amount of attention during the winter months, 

 even though covered with a tongue-and-groove wooden cover. No nuisance was 

 produced during the summer months by the dosing of the uncovered sand bed 

 with the tank effluent. The growth of weeds on the surface did not seem to 

 have an unfavorable effect upon the operation of the sand bed." 



The management of liqu^ and solid manure in Belgium, H. Vendelmans 

 (Joiir. Bd. Agr. [London^, 23 (1911), No. 12, pp. 1208-1221, figs. 6).— Tanks 

 and pits for the conservation of liquid and solid manure are described and 

 illustrated as developed by experience in Belgium. 



Tanks for liquid manure are best placed immediately under the standing 

 place of the cattle, occupying the full width and running the entire length. A 

 depth varying from 32 in. at the shallow end to 35 in. at the outlet is consid- 

 ered sufficient. Walls of one thickness of solid 9-in. bricks set in cement 

 mortar are sufficient without foundation. The floor is of bricks waterproofed 

 with cement. 



Manure pits are made to provide easy handling of the manure and shelter 

 from sun, rain, and wind, to avoid white molds, and to improve the ripening 

 process and hygienic conditions. A water-tight, solid manure pit of brick or 

 cement is made against the wall of the cow house, running its entire length. 

 The capacity is calculated on the quantity of manure produced between two 

 successive emptyings and is varied by varying the width. The pit is sunk 

 into the soil about 32 in. to avoid atmospheric influences. 



State highway mileage and expenditures for the calendar year 1916 (U. 8. 

 Dept. Agr., Office Sec. Cire. 74 (1917), pp. 8, fig. i).— This circular states that 

 " cash expenditures on the rural roads and bridges in the United States in 

 1916 amounted to $272,634,424. To this should be added the value of the 

 statute and convict labor, which can not be fixed with any great degree of 

 accuracy, but probably amounted to not less than $15,000,000, thus making the 

 grand total expenditure for the year $288,000,000. ... At present there are out- 

 standing more than $400,000,000 of road and bridge bonds and long-term war- 

 rants, maturing at the rate of about $20,000,000 per year and requiring about 

 an equal amount for the payment of interest charges. . . . More than $40,- 

 000,000 of new road and bridge bonds are now being issued annually. 



" The public rural roads of the United States at present have a total length . 

 of 2,455,761 miles, of which about 287,000 miles, or 11.6 per cent, are improved 



