Paraffin versus enamel: optimum nuimber of sampling points: improvement of tubular balance

Hard varnishes, such as Risch-Rasch, on the inner surfaces of duraluminum wear out unevenly and result in rough surfaces. Removal of the varnish with strong caustic is inadvisable with soft duraluminum; removal with alcohol or paint remover is time consuming. Tubes coated with paraffin last one season and are adequate to prevent clogging. Spare lower joints may be carried along when heavy service is anticipated.Devore recommends 16 sample points in snow courses. Six or seven sampling points in snow courses have been found adequate in the King’s River watershed. Fewer samplings are desirable in order to preserve the tube coating and to reduce time and labor costs.It is recommend that the 20-ft-capacity scales of samplers be graduated below the 140 inch mark to 220 in. Such an adjustment would require only the extension of graduations to the end of the tube, and would increase the total capacity of the tube by 82 inches.John T. Ryan exhibits a graph of data collected from a test of the Bureau of Agr. Engrs. Tubular Scales No. 388 indicating excellent accuracy if the scales were calibrated from 140 in. to 220 in.