1897] MICROSCOPICAL JOURNAL. 305 



tion and making wells possible. Thus in localities where 

 artificial filter beds are impracticable it may be possible 

 to resort to wells with similar results. Experimental 

 borings are required in order to determine whether the 

 quantity of water is adequate and whether the soil through 

 which it percolates is adapted to secure its purification. 

 This being done and the system established, the inter- 

 mittent action of the pumps, running a part of each day 

 like intermittent filtration-, yields a much purer supply 

 than could be had in any other way. A point to be 

 guarded against is the infl.ux of surface water, which is 

 specially liable to contain malarial infection as well as 

 other impurities. To this end, numerous small wells, 

 consisting of iron pipes put down to the proper depth 

 and having perforations over a space of six or eight feet 

 from their lower extremities, covered with fine wire 

 gauze, may be employed. Another plan that may serve 

 is to have a siugle large well, twenty feet or more in 

 diameter. A convenient method of construction of such 

 a well is by the use of a curb, built up in a hexagonal or 

 octagonal form, of plank laid flatwise and spiked one upon 

 the other in layers. If such a curb be made, slightly 

 smaller towards the top, it can be carried down success- 

 fully through almost any sort of soil and stoned up. 



It has been thought best to enter somewhat into such 

 details as have been indicated, because they illustrate the 

 principles involved in improvement of water supply, 

 especial reference having been had throughout to locali- 

 ties v/hose resources are limited. The adaptation of 

 laboratory results to practical uses is the point specially 

 sought to be accomplished in this brief summary. The 

 sanitary engineer, the practising physician and the 

 skilled microscopist are upon common ground in these 

 studies. 



At the present stage of progress it must be admitted 

 however, that serious imperfections are unavoidable in the 



