286 EXPEKIMENT STATION RECORD. 



The object-lesson road is the ruetliod chosen for making available the results 

 of investigations of the office in road construction. " Briefly stated, the purposes 

 of object-lesson roads are, first, to introduce among local road builders correct 

 methods of construction and maintenance; second, to demonstrate the advan- 

 tages of a properly built road in order to stimulate public sentiment for road 

 improvement and ai'ouse a spirit of jirogress ; third, to afford a basis for esti- 

 mating cost of additional road construction, which may be subsequently carried 

 on by the county or community ; fourth, to demonstrate the availability and 

 relative value of local materials as far as practicable." 



Tables are given showing the location of object-lesson roads constructed in 

 1904-5 and 190.3-C, showing the kind and source of material, the distance trans- 

 ported, the dimensions of the road, the cost per square yard and per mile, and 

 the cost of labor per day. Reports regarding the px'esent condition of a number 

 of the roads built are included in the paper. 



A rotating traction plow, C. Lumia (CoJtivatore, 53 (1907), Xo. 17. pp. 

 529-532, flff. 1). — The author describes a very unusual type of plow in which the 

 ordinary iilowshare is replaced by a pair of auger-like screws which precede 

 the machine and are rotated in opposite directions with respect to each other 

 as the machine moves forward. The machine is operated by a gasoline motor 

 and is self-propelling. It is claimed to possess certain advantages in giving the 

 soil a more thorough stirring than is possible with the ordinary plow. Turning 

 and operating the plow leaves Jy of the area of the field upon which it is used 

 unplowed. and in a 10-hour day it is claimed that 2.5 acres may be plowed to a 

 depth of 8 in. in compact soil at a total expense of $7.60, with gasoline at a price 

 equivalent to 40 ets. per gallon. 



Corn harvesting machines, M. Kingelmann (Jour. Agr. Prat., n. ser., IJf 

 (1907), yo. 32. pp. 172-175, figs. 6). — Various simple American devices for this 

 puri)ose are described. ■• 



On the peculiarities of denatured alcohol (Mascli. Ztg., 5 (1907), No. 7, p. 

 80). — Apparatus using denatured alcohol such as motors and incandescent 

 lamps, is often injured and its working parts corroded by the products liberated 

 in the process of combustion. The question has arisen as to which of the mate- 

 rials in consideration, the alcohol itself with its impurities such as aldehyde 

 and ether, or the denaturing materials like methyl alcohol, benzine, etc., is the 

 agent responsible for the corrosive effect. The denaturants have formerly been 

 held in suspicion, but recent investigations by Lindet, Heinzelman, and others 

 have shown that the usual impurities of undenatured alcohol, viz, aldehyde and 

 ethyl acetate, may cause corrosion to a greater or fess degree, though the time 

 required to effect noticeable injury is longer than with the denatured alcohol. 

 The effects of using the latter are briefly summarized as the formation of 

 acetic acid, the clogging of the inlet and outlet valves, corrosion of the motor 

 cylinder, clogging and corrosion of burners, hardening of wicks, and early 

 destruction of the wire parts of incandescent burners. 



The means recommended to obviate this trouble is the removal of the alde- 

 hyde and acetates to the greatest possible extent and the use of benzine of a 

 not too high boiling point. 



RURAL ECONOMICS. 



Freight costs and market values, F. Andrews (U. S. Dept. Agr. Yearbook 

 1906, pp. 371-386). — The author discusses the cost of hauling from farms and 

 the prevailing freight rates on cotton and wheat in 1906 to the principal ship- 

 ping and exporting points in the United States, the ocean freight rates to the 



