1916] RURAL ENGINEERING. 685 



Douglas fir bridge stringers, subjected to the boiling-under-vacuum process of 

 creosoting, was five-sixths of its original strength." 



Automobile reg'istrations, licenses, and revenues in the United States, 

 1915 {U. S. Dcpt. Ayr., Office Sec, Circ. 59 (1916), pp. 15, fiii. i).— This bulle- 

 tin contains tabulated data on the following: Motor- vehicle registrations, 

 licenses, and revenues, 1915; motor-car registrations and gross motor-vehicle 

 revenues, 1913-1915; motor-vehicle registration and license fees in force Janu- 

 ary 1, 1916; and administrative provisions in force January 1, 1916, affecting 

 motor-vehicle registrations, licenses, and revenues. 



" During 1915 the total gross revenues derived from the registration of 

 motor vehicles and the licensing of operators, chauffeurs, dealers, etc., amounted 

 to $18,245,713. ... Of the total revenue collected during 1915 practically 

 90 per cent was applicable to road work, and of this slightly over 70 per cent 

 was placed more or less directly under the control and supervision of the state 

 highway departments. . . . 



" The number of motor vehicles registered under the general designation of 

 automobiles, motor trucks, and commercial vehicles in continental United States 

 during 1915 amounted to a total of 2,445,664. The total road mileage of the 

 United States outside of incorporated towns and cities is approximately 2,375,- 

 000 miles. There is, therefore, an average of slightly more than one motor car 

 for each mile of rural public road in the United States." 



Prevention of pounding in kerosene engines, J. A. Moyee and J. P. Caldee- 

 wooD (Ann. Rpt. Perm. State Col., 1914, pp- 109-117, pis. 10). — Experiments 

 with a 4-cycle hit-and-miss governed oil engine with a cylinder bore of 6.75 

 in., a 10-in. stroke, and a clearance of 22.9 per cent to determine the cause of 

 pounding and methods for its prevention are reported. The carburetor was an 

 experimental spraying type. 



It was found that pounding was increased by increasing the temperature of 

 the gas, increasing the temperature of the jacket water, and increasing the 

 spark advance. Pounding was decreased by increasing the fuel rate and in- 

 creasing the water injection. " In attempting to draw conclusions from these 

 results it is practically impossible to state whether this pounding was produced 

 by cracking of the heavier hydrocarbons or by high flame propagation, but 

 from a practical point of view the conditions affecting eitiier of these causes 

 are identical, and inasmuch as we can prevent or govern this pounding by the 

 use of water and rich fuel mixtures, meaning a relatively large amount of 

 kerosene used compared with the air, it seems that differentiation as to ulti- 

 mate cause is not necessary, ... In using gasoline under conditions of fuel 

 mixture and water temperature similar to those imposed upon kerosene in 

 these tests the pounding and the indicator cards are identical with those of 

 kerosene. These tests show also very clearly that the temperature of the fuel 

 mixture at the firing period is the condition that governs the quality of the 

 pounding." 



Directory and specifications of leading makes of trailers {Farm Machinery, 

 No. 1284 (1916), pp. 18, 19). — This list contains the names and specifications of 

 75 types of trailers of 30 different makes. 



Official tests of mechanical cultivation, Ringelmann (Jour. Agr. Prat., n. 

 ser., 29 (1916), No. 4, pp. 7^, 75). — The more important results of tests of 

 several outfits are summarized in the following table. 



