EURAL ENGINEERING. 583 



extract of the glands but requires a definite period for development. It is not 

 stable and gradually disappears from the extract. 



The action of a coal-tar disinfectant on hog cholera virus, W. E. King 

 and 11. H. Drake (Join: Atncr. Vet. Med. Assoc, ^8 (1915), No. 3, pp. 315, 

 S16). — ^The results of experiments here reported in tabular form indicate that 

 highly virulent hog cholera virus (in the form of serum from cholera infected 

 hogs) exposed for 5 minutes to the action of a 2 per cent solution of Kreso is 

 rendered inert. 



Lupinosis of horses and the treatment, A. D. Knowles (Jour. Arner. Vet. 

 Med. Assoc., 48 (1915), Nn. 3, pp. 286-303, figs. 3). — This account of lupinosis 

 includes reports upon experiments with a number of cases and the nature of 

 the lesions caused. It is stated that some of the animals which were placed on 

 the artificial Carlsbad salts treatment a few weeks previous were making 

 satisfactory improvement at the time of writing. A list of 10 references to the 

 subject is appended. A discussion entered into by several follows (pp. 

 300-303). 



Blackhead in turkeys, R. Graham and L. R. Himmelberger (Kentucky Sta. 

 Circ. 7 (1915), pp. 35-4-'}, figs. 3). — A popular account. 



RURAL ENGINEERING. 



Trenching machinery used for the construction of trenches for tile drains, 

 D. L. Yaknell (U. S. Dcpt. Agr., Farmers' B%il. 698 (1915), pp. 26, figs. 15).— 

 This publication describes the types of trenching machinery used for the con- 

 struction of trenches for tile drains, under the four general classes of (1) 

 plows and scoops, (2) wheel excavators, (3) endless-chain excavators, and (4) 

 scraper excavators, and discusses the limiting conditions of operation and the 

 factors affecting the cost of trenching. Back-filling and tile-laying devices are 

 also described. 



The requisites of a good trenching machine are stated as follows: (1) It 

 must operate efficiently through various kinds of soil, (2) it must be capable of 

 cutting true to grade, and (3) it must work for long periods without breaking 

 or otherwise getting out of order. Good materials, proper proportioning of 

 strength, and simplicity of construction are also desirable. 



It is pointed out that while there is not a great difference in the cost of 

 trenching by hand and machinery, the advantage of the latter method is in the 

 shorter time required to install drains and the less trouble in securing the few 

 workmen needed. 



" In selecting a trenching machine the prospective purchaser should consider 

 carefully the amount of work to be done by it, the dimensions of the trenches 

 to be dug, the nature of the soil to be excavated, and other conditions of work. 

 The wheel type of excavator is most generally used for installing farm drains, 

 probably owing to a lower cost for the smaller sizes than the cost of the chain 

 type. Machines of the latter kind have gi-eater range in size of trench than 

 wheel excavators of the same weight and seem to be better adapted for work 

 when there is a great deal of 8-in. tile and larger. When the greater portion 

 of a job is small tile at ordinary depths, the excavator should be suited to the 

 major part." 



The weight of the excavator is important in digging soft earth and may make 

 necessary the use of apron tractors instead of the less expensive wheels. " Some- 

 times internal-combustion engines are preferred to steam equipment because 

 • they weigh less. Internal-combustion engines are also quite popular for the 

 smaller machines because the number of men required for operation is less, 



