1917] RURAL ENGINEERING. 87 



The destruction of mosquitoes and their breeding places and the provision of 

 clean and adequate supplies of drinking water seem to have been the greatest of 

 the problems encountered by the author in his work in tropical rural sanitation. 



The treatment of sewage by aeration in the presence of activated sludge, 

 K. Baktow (Trans. Amer. Inst. Chem. Engin., 8 (1915), pp. 119-lSl, figs. 6).— 

 This is a general review of the experience of the author and others. 



Methods of clearing logged-off land, C. H. Shattuck (Idaho Sta. Bui. 91 

 (1916), pp. 59, figs. 40). — Tests of methods of clearing logged-ofE lands in Idaho 

 are reported. 



It was found that methods emploj^ing explosives cost from $35 to $150 per 

 acre and frequently required much leveling. Such methods were found to take 

 out stumps completely, break up hardpan, and bring land into cultivation 

 quickly. On the other hand the cost was found to be prohibitive for the poorer 

 farmers and the fertility of the soil was frequently injured by clay, sand, rock, 

 and gravel brought to the surface. 



Charpitting was found to cost from $10 to $75 per acre and was one of the 

 cheapest methods, as it required no apparatus. Charpitting was not a success 

 in sandy soil, however, and required constant attention and much labor. Burn- 

 ing from the center of the stump by boring cost about the same as charpitting 

 and required less labor and care. Burning from the center by sawing the stump 

 off and skidding it up generally cost less than charpitting and required less care 

 than chai-pitting or burning from the center by boring. Another advantage of 

 this method is that the fire is kept going by gravity. The general advantages 

 of burning methods were found to be that little capital and only a small amount 

 of inexpensive apparatus are needed, less leveling is required than by the use 

 of explosives, and much debris is disposed of. 



Methods employing hoods on outside charpitting, bored stumps, and sawed off 

 stumps cost slightly more than straight charpitting. Such methods were found 

 to require less work and care after the stump was fired and if a condenser was 

 used part of the by-products could be saved. 



Methods employing stump pullers on cracked stumps, small stumps, and on 

 small standing timber generally cost more than charpitting and required more 

 equipment. Less leveling was required, the cost of powder was reduced where 

 stumps were cracked, and fewer snags and roots were left than by burning. 

 Methods employing donkey and traction engines on small trees, small stumps, 

 and cracked stumps generally cost much more than charpitting and required 

 skilled operators and expensive machinery. These methods were found, how- 

 ever, to work rapidly in young standing timber or on small stocks of heavy 

 stumps. Little leveling was required, the cost of powder was reduced, and few 

 snags and stumps were left in the soil. Another advantage was that the stumps 

 were piled, preparatory to burning. 



Methods employing pasturage were found to be the cheapest of all methods 

 and the best of all methods where time is not an important factor. 



Prevention of the erosion of farm lands hy terracing, C. E. Ramser (U. 8. 

 Dept. Agr. Bui. 512 (1917), pp. 40, pis. 9, figs. iS).— This bulletin is based upon 

 the results of surveys, observation, and a study of terraced fields in the best 

 terraced sections of the country, and deals with terracing as a means of pre- 

 venting the erosion of hillside land, describing the different types of terraces, 

 pointing out the applicability of each to the various kinds of soil and topog- 

 raphy and discussing the principles of terrace design. 



" The terraces in use in this country are of two general classes, the bench 



terrace and the ridge terrace. . . . The disadvantages of the bench terrace are 



that it can not be crossed by modern farm machinery ; the banks can not be 



cultivated, while each bench must be cultivated as a separate field ; weeds and 



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