19161 RURAL ENGINEERING. 887 



obtained with the ininiiuuin (0.015 in.) gap, and miiiiniuin values witli a gap 

 of O.OG in. At velocities loss than 0.1 ft. per second the effect of a variation in 

 this width becomes very pronounced. 



"Abnormally high values of C at moderately low vokKiLu>.s are to be attributed 

 to errors in tlie throat gage reading, due to the accumulation of air at the 

 throat. Such high values are only to be anticipated in a meter in which the 

 throat pressure is le.-^s than atmospheric, and probably only where indei>eiident 

 measuring columns are us«>d at entnmce and at throat, and where conununica- 

 tion between throat and measuring coluum takes place through a circumferen- 

 tial gap surrounding the throat. Where a U-tube gage or any of its modifica- 

 tions has been used there would appear to be no record of any such high values 

 of C, and such a device should be used where there is reason to anticipate 

 negative pressures. 



"An examination of all available data shows that, whatever the conditions 

 under which a meter may be op(Tating, the value of C varies within narrow 

 limits so long as the pipe line velocity exceeds 1 ft. per second. This coetficient 

 may vary from about 0.96 to slightly over unity. In the normal meter ol 

 moderate or large size a value of 0.99 will pro))ab]y give the value within 2 per 

 cent for any velocity exceeding 1 ft. per second. Where essential that the 

 records for lower velocities should be accurate, this can only be insured by a 

 calibration of the meter." 



Pumps for the irrigation of small areas, B. Dibble (Jour. Electricity, 57 

 {1916), No. 4, pp. 65-67, fiys. S). — Factors to be observed in the selection of 

 centrifugal pumps for the irrigation of small areas are discussed. 



Experiments upon the purification of sewage and water at the Lawrence 

 Experiment Station, H. Vf. Clark and G. O. Adams (Ann. Rpt. Bd. Health 

 Mass., 46 (1914), pp. 297-346). — These experiments include special studies "of 

 the relative efficiency of trickling filters of dilferont depths, of the disposal 

 and utilization of sewage sludge, of the purification of sewage by aeration 

 in tanks containing layers of slate upon which 'growths ' form, etc., and of the 

 purification or disinfection of water by means of liquid chlorin." 



Sewage disposal for isolated residences, C. G. Gillespie (Cnl. Bd. Health 

 Spec. Bui. S (1916), pp. 2S, figs. 4). — This bulletin describes the ^ptic tank 

 and tile absorption method of residential sewage disposal. 



" The tank must be located judiciously, so that prevailing winds will carry 

 odors in a direction away from dwellings and so that wells and watercourses 

 will not be polluted by the effluent. Under ordinary conditions, for safety, 

 200 ft. should separate the tank and the nearest well, watercourse, homes, or 

 highway." 



Sanitation in the mountains, C. G. Gillespie (Cal. Bd. Health ."^pec. Bui. 10 

 (1916), pp. 3-20. figs. S).— This bulletin deals with the sanitary privy and septic 

 and Imhoff tanks for the disposal of sewage in mountain resorts. 



Engineering operations for the prevention of malaria, F. D. Evans (Min- 

 utes Proc. Inst. Civ. Engin. [England], 200 (1915), pt. 1, pp. 2-61, figs. 12).— 

 This is a presentation of the details of these operations. 



Terracing in Texas, J. G. Olsen (Agr. and Mech. Col. Tex. Ext. Serv. Bui. 

 B-2S (1916), pp. 3-32, figs. 27). — This bulletin describes and illustrates methods 

 of erosion prevention practiced in Texas. 



The use of dynamite in clearing land, E. Seckest (Mo. Bui. Ohio St a., 1 

 (1916), No. 8, pp. 236-239, figs. 2). — The cost of dynamiting white oak. beech, 

 hickory, chestnut, black oak, maple, cherry, and black gum tree stumps ranging 

 in age from six months to 25 years and in diameter from 6 in. to 42 in. are 



69107°— No. 9—17 7 



