AGRICULTURAL ENGINEERING. 827 



aboratorv is to obtain results, by means of appropriate tests on small samples, which 

 will agree sufficiently well with the results of practice to aid the road builder in 

 selecting the most suitable materials from those available for his work." 



The methods and tests used in the laboratory, which are described and for which 

 data are in some cases given, include the abrasion, cementation, absorption, specific 

 gravity, and weight per cubic foot, hardness, and compression and tensile strength 

 tests of rock and gravel; and "rattler," aljsorption, cross-breaking, and compression 

 tests for paving brick. In tests of cement the methods of the American Society of 

 Civil Engineers are followed. The petrographic and chemical methods used in the 

 examination of rocks for the purpose of classification are also described. The results 

 of examinations of a large number of materials from different parts of the United 

 States are given. 



As regards the general cpiestion of the practical application of laboratory results 

 the authors say: 



" The proper interpretation and application of the results obtained in the labora- 

 tory are quite as important as the general accuracy and appropriateness of the tests 

 themselves. It is 2)robal)le that many engineers and others interested in the subject 

 of road building who have found time to examine the question only superficially 

 have misunderstood the bearing and value of road- material testing. In all cases the 

 results obtained in testing materials of construction are of relative rather than abso- 

 lute value. Even quite a large variation in the results yielded by different test 

 pieces of the same sample should not condemn the j^ractical value of the figures if 

 they are properly applied and interpreted. . . . 



"Given a num))er of materials for laboratory examination, it is not pretended that 

 an actual practical grade of excellence can be established. On the other hand, if 

 more than one material is available, it is quite possible for the laboratory to jwint 

 out which one would yield the best results, both as to immediate excellence and 

 length of life under known conditions of climate and traffic." 



The farm railroad (tramway) and the results obtained with it on the 

 Buhlendorf estate, Reichert {Fiihling^s Landw.Ztg., 52 {1903) , Nos. 22, pp. 797-817, 

 fign. 17; 23, pp. 852-864, figs. 7). — The advantages of farm tramways in general are 

 explained; the installation on the Buhlendorf estate, which is largely devoted to 

 sugar-beet growing, is described; and the uses made of the tramways on this estate 

 and the profits resulting from their use are discussed. 



An example of thin macadam road construction along the Charles River, 

 Massachusetts, J. A. Holmes {Engineer. Kews, 51 {1904), -Vo. 2, pp. 32, 33, figs. 3). 



The construction of roads, paths, and sea defenses, F. Latham {London: 

 Sanitary Pub. Co., Ltd., 1903, pp. IV+ 221, figs. 57). 



The construction of terrades, E. Leplae {Rev. Gen. Agron. [Louvain'], 12 

 {1903), No. 10, p)p. 435-442). — This is an extract from a course of instruction given 

 at the agricultural institute of Louvain. 



The possibilities of irrigation in South Africa, C. D. H. Bkaine {Agr. Jour. 

 Cape Good Hope, 24 {1904), No. 1, pp. 48-58). — A general discussion of this subject. 



Preliminary plans and estimates for drainage of Fresno district, Cali- 

 fornia, C. G. Elliott {Cdifornia Sta. Rpt. 1902-3, pp. 57-64, dgms. 2). — A reprint 

 of Circular 50 of this office (E. S. R., 15, p. 94). 



The Cache River drainage survey, A. H. Bell {Engineer. News, 51 {1904), No. 

 5, pp. 115, 116). — This is a brief account of the preliminary operations of a commis- 

 sion appointed by the Governor of Illinois under the provisions of a recent bill 

 passed by the legislature of the State for a survey of the Cache River to ascertain the 

 practicability of straightening and deepening the channel of the river for the pur- 

 pose of preventing overflow of the bottom lands and for the drainage of these lands. 



The mitigation of floods in the Hunter River, J. H. Maiden {Jour, and Proc. 

 Roy. Soc. Neiv South Wales, 36 {1902), pp. 107-131).— This article discusses the causes 



