THE WATER-SUPPLY OF TOWNS IN THE TROPICS 299 



And then, turning to well and spring waters, lie remarks : — 



" A good wafer should contain no ftecal bacilli in 20 c.c. 



" No Glass I. in 100 c.c. Total colonies under 50 per c.c. 



" We are for the present unable to give any other standards than this." 



Now it may be thought I have dealt at too great length with Clemesha's work, but 

 it was essential to do so as one is anxious, if possible, to obtain expert opinion on it.* 

 It has been no easy task to keep the resuni6 even within these limits, but I trust that 

 all salient points have been considered and his arguments made clear. We have now- 

 reached the point at which I was aiming, namely the fact that Clemesha confesses that he 

 cannot tell how far his method is applicable to the waters of springs and wells which are 

 not exposed to the direct action of sunlight. He admits that in these cases the question is 

 much more complicated than when one is dealing only with surface waters, the difficulties 

 being (i) to estimate the importance and significance of organisms that remain alive iu the 

 soil for long periods and (ii) to be quite certain when a pollution is caused by surface 

 contamination washed down through cracks or through a porous soil. 



The quantitv of fascal pollution, he regards as of paramount importance in the , 



° '■ '- Importance of 



case of well-water, and the standard he adopts has been given. This of course applies quantity in 



only to surface wells. He tells us nothing regarding deep wells, and here it is that P°"""°" 



I hope to make good a deficiency and to show that in Khartoum, at least, the standard 



of Houston and Savage has proved itself a reliable guide in an interesting and difficult 



problem. I hold no brief for Major Clemesha and his work. It requires confinuation 



and may be refuted. Captain Archibald has been workingf on similar lines with river 



and shallow well-water in Khartoum where, however, conditions differ considerably 



from those in Madras. But whatever may eventually be proved, there can be no doubt 



that the Indian work is in the right direction and that it has been carried out with 



much care and devotion and in an eminently sensible and scientific manner. 



To revert to Khartoum. At the time when it became necessary to embark upon 

 water work thei-e, Clemesha's researches had not appeared, and one had to proceed 

 more or less on the old familiar lines. 



I have mentioned the Blue Nile, a river clear when low, with very palatable water 

 of an agreeable softness and colour, and comparatively pure save where fouled from the 

 bank at a town or village. I need not enter here into the chemical composition of its 

 water.! In flood time it is, of course, muddy, laden with silt and washings from the ^, „, .,., 



^ The Blue Nile 



Abyssinian mountains. Some records of bacteriological observations are available though water 

 several were destroyed in a fire. Those existing show that in January, 1907, at low- 

 Nile, the number of organisms in 1 c.c. of the w-ater taken close to the bank above the 

 town was between 300 and 400 (agar count at 37 C, 48 hours' incubation), while in a 

 sample taken from the centre of the stream at Buri in February, 77 organisms were 

 found per 1 c.c. In May, with the river rising, a sample taken from mid-stream, 

 opposite the Gordon College, gave 84 organisms. Other observations show that the 

 counts vary considerably and close to the bank as many as 700 colonies per 1 c.c. have 

 been found, while B. c.oli of an excretal and " flaginac " type is commonly present iu 

 from -5 to 1 c.c. of water taken close to the bank, but is not found in less than 5 c.c. 

 of water from mid-stream. Formerly, the Nile served as the chief source of supply so 

 far as drinking-water was concerned, and so long as the w-ater was not stagnant did not 



* This is now to some extent forthcoming in a recent paper by Brevet-Colonel E. H. Firth (Journal Royal 

 Army Medical Corps, November, 1910/ 



t Vide page .319. 



X Fide paper bv Dr. Beam in Second Report of these labor.itorios, p. 207 rf sni. Also, and in fuller 

 detail, in the Third Report, p. .386. 



