11G 



MOSQUITO ERADICATION 



wire from the blasting machine. The charges are then exploded 

 simultaneously by operating the machine. 



For larger ditches, the loading may be in deeper holes and with 

 an explosive of greater strength, or parallel rows of charges may 

 be employed as already described in the case of propagated blast- 



f 



Duplet, leadinq ir/re h b/ashng machine 

 ,s^ (Zonnecf/nq wipe, fo fead/hg tvtnz 

 fi/asf/bg cap iv/ms connecfed\^ 



i ^-' uiasnng cap nrrcs connt 



-Grac/e qf proposed f//'/ch- 



Primed dynamife. 

 cartridges 



Fig. 76. — Loading for blasting ditch, having only a single row of holes, by 



electrical firing. 



ing. Where very deep ditches are needed, a wide shallow ditch 

 should be blasted first and then a row or two of holes should be 

 blasted in the bottom of this ditch. 



75 (>/asHng machine. 



Fig. 77. — Flan of loading for blasting a ditch, having 2 rows of holes, by elec- 

 trical firing. 



ADVANTAGES OF BLASTING DITCHES 



The personnel required for blasting ditches is small. One 

 laborer should make the holes, another distribute the dynamite 

 in them under the direction of the foreman, a third and fourth 

 transport the dynamite to the scene of the blasting and a fifth 

 and sixth clean out the ditch after the blasting. An experienced 

 blaster should be in charge of the work. 



Under favorable conditions, the work may be carried on at the 

 rate of 100 to 200 feet per hour by the propagation method with 

 the crew indicated above, omitting from consideration, of course, 

 any preliminary clearing that may be required. 



Costs of ditching by dynamite vary, of course, with the 

 character of the soil, size of the ditch and number of roots and 

 stumps. At six different extra-cantonment jobs in 1918, costs 

 per lineal foot were: 13, 14, 28, 18, 12 and 33 cents. Wherever 

 comparisons with hand ditching in swamps were made, it was the 

 consensus of opinion that blasting was cheaper. 1 



1 Transactions of The First Annual Conference of Sanitary Engineers, 

 U. S. Public Health Service, 1919. 



