RURAL ENGINEERING. 787 



Land drainage in Maryland. J. K. IlAswr.r.L (Maryland l^ta. Bui. ISG {1914), 

 pp. 69-ll:i, fi<;-s. !>). — This bulletin is baseil upon the work of the Drainage 

 Investigations of this Ofiice in the State of Maryland. Its purpose "is to show 

 briefly what properly constructed drainage improvements have accomplished 

 and will accomplish in developing farm lands in the State, and to offer sugges- 

 tions that may assist in the proper application of drainage in all parts of 

 Maryland." 



There are 517 square mih's of swamp and marsh land in the State, the 

 greater part of which occurs in the 2.(i."iO square miles of coastal plain. Under 

 " bcnetits of drainage" the results obtained in different localities in the State 

 are briefly reported. The author also takes up briefly land drainage for mos- 

 quito control. 



In an appendix is given the text of the Maryland drainage law. 



Concrete in drainage and irrigation, P. T. Libberton (Trans. Amer. Soc. 

 Agr. Engin., 7 (1913), pp. 135-l.'i5, figs. 6). — The author discusses the use of 

 concrete in irrigation and drainage structures and points out that its successful 

 use iu these depends largely on the proper selection, proportioning, and mixing 

 of materials. 



Progress report on cause of disintegration of cements by alkalis, K. Steik 

 (Wijdiiiing Std. Rpt. 1914. PP- ^-'/<'^-/''^'. figs. 11). — In the course of this work the 

 following comiwunds have been isolated: (1) Calcium sulphate, (2) calcium 

 hydroxid, (3) calcium carbonate, and (4) one silicate of which the composition 

 has not yet been determined. 



" The calcium sulphate hydrated salt was found to be a reaction product 

 between cement and the sulphates of magnesium and sodium. This salt was 

 found deposited in crystalline form from solutions of varying strength, from 1 

 per cent to 10 per cent. The crystals were iu all cases found on the surface 

 of the blocks of cement, deposited either as single crystals or as groups of 

 crystals X'adiating from a center. ... In some cases the sulphate of calcium 

 was deposited in amorphous form. This was more noticeable in cements low 

 in lime content. The microscopic examination of the cements which had a 

 great abundance of crystals on the surface did not show their presence inside 

 the cement blocks. The same was found to be true in case of the other com- 

 pounds mentioned. . . . 



" The calcium hydroxid was obtained from cement immei'sed in solutions of 

 chlorids of magnesium and sodium, also from solutions containing both these 

 chlorids. Also this compound was deposited on the surface in ci'ystals about 

 i in. wide and about 1.64 in. thick. . . . 



" The calcium carbonate was obtained iu amorphous form only from cements 

 iu solutions of sodium carbonate." 



Further studies were made of the effect of alkali salt solutions on the strength 

 of cements. It was found that high silicia cement when immersed in a 5 per 

 cent solution of equal parts of sodium carbonate, sodium chlorid, and sodium 

 sulphate was reduced in tensile strength 3.5 per cent after 12 months and 14.2 

 per cent after 20 months and was increased in compressive strength 10 per cent 

 after 12 months and 1G.3 i>er cent after 2G months. 



The tensile strength of neat Portland cement when immersed in a 5 per cent 

 solution of sodium chlorid, sodium sulphate, magnesium chlorid. and magnesium 

 sulphate was increased 101.3 per cent after 12 months and decreased 13.3 per 

 cent after 26 months and the compressive strength was increased 46 per cent 

 after 12 months and decreased 25.7 per cent after 2G months. In a similar set 

 of tests increases in strength were observed in all cases. 



93681°— No. S— 15 7 



