RURAL ENOTNEERTNG. 781 



as ofcurrhif,' in i)i.i;c'ons in isnc. 'I'lic nntlior lias niado a study of tho anatomy 

 and biology of the pest, which are described in the present article. The parasite 

 is found most commonly in the connective or subcutaneous tissue about the 

 trachea and el.sewhere in the retiion of the nci-k. 



RURAL ENGINEERING. 



Can the yield of crops be increased by irrigation under the climatic con- 

 ditions of Germany? Gkklach (Mitt. J)ti(t. LaiKlir. (Icscll.. ,il {li)()6), A o. JjO, 

 l>l). SSJ1-SH6). — The writer takes up this question ai a general way, giving some 

 results already found and suggesting lines along which research should con- 

 tinue to determine if irrigation is practicable and profitable in (Jerniany. Ger- 

 man experiments are quoted which give the absolute water re(iuirements of 

 different crops per pound of dry substance, as follows: Wheat. 838 lbs. of 

 water; rye. 'A~j.\ lbs.; oats, :j7»! lbs.; barley, 310 lbs.; peas, 273 lbs.; I'ed 

 clover, 310 lbs. 



From exi)erinients with and without fertilizers, it is concluded that irrigation 

 is of little value in increasing the yield when there is a deficiency in plant-food 

 material. Thus, without fertilizers, 1,665 lbs. and 3,330 lbs. of water resulted 

 in an increase in yield of 1.48 lbs. and ^.7,^ lbs. of dry substance, respectively; 

 :iM(l with fertilizers, 2.89 lbs. and 7.!> lbs., resjiectively. 



The rainfall necessary to produce a nox'mal development of field cTops in 

 Germany is given as follows : Winter gi'ain, 23.() in. per year ; barley, 20.8 in. 

 per year ; oats, 2ij.2 in. per year ; potatoes and beets, 23.6 in. per year. 



A table is also given showing the ideal distribution of rainfall through the 

 year by months. The results are not applicable for all parts of Germany, since 

 for I'entkowo in l!»0.>-4 the following crops were grown with only 15.(i.") in. of 

 rainfall: Rye, 3,740 lbs. per acre; wheat, 4,460 lbs. per acre; oats, 3,740 lbs. 

 per acre. 



With regard to the most successful wa.v of retaining soil moisture, the author 

 states that it is doubtful if much can be added to the present knowledge of the 

 effects of cultivation and tillage. He thinks, however, that in case of drained 

 lands the common German practice is to drain too thoroughly, particularly in 

 spring and summer, in localities having but little precipitation during these 

 seasons. 



On automatic puddling of channels, [II. Maksii] {[Froc] Irrir/. Coiif.. 

 i^inila, 190.), /, pp. liiO-lSS, figs. 4). — The necessity is stated of providing some 

 means of lessening the 50 to 60 per cent loss in water between the canal head 

 and the fields. Lining the channels by manual labor is not considered prac- 

 ticable, since it is estimated that the lining of a 3-ft. lateral would cost about 

 $2,.500 per mile and woukl lead to a return of only .$75 per mile. In tin- 

 writer's opinion the only practicable method is the puddling of the perimeter 

 of the channel by the running water. This he effects by giving tlie main 

 canals a slope of about 0.5 or 0.6 ft. per mile. Deposition of silt in distribu- 

 taries is said to be due more to excessive erosion in the main canals than 

 lack of velocity in the distributaries. 



Instances of the success attendant upon reduction of canal slojie are given. 

 In one case on the Ganges canal the breaking up of a rapid slope probably 

 is responsible for a saving of 19 cu. ft. per second out of a total of 42 cu. ft., 

 the net outcome being that an expen.se of about $10,500 produced a capitalized 

 economy of water amounting to $190,000. In another instance a channel with 

 a gravelly betl experiencetl a loss of 27 per cent in the discharge when water 

 was first turned in. The percolation thereafter diminished to l.S per cent, 

 due to gradual silting up. 



