218 REPORT— 1876. 



it is com or couch grass, rats or rabbits. On this subject I thiiik both the engineer 

 and the chemist -n-ill but grope in the dark until the biologist comes to their aid, 

 working statistically with liis microscope as well as observing particular develop- 

 ments. Whether any observers are yet prepared by preliminaiy knowledge for such 

 investigations I know not, but sure I am that the need of them has come. 



It may be some consolation to the timid or fastidious among my listeners to be 

 assured, first, that only a few organic germs are capable of hurting us ; and, 

 secondly, that an overwhelming proportion of the germs of life perishes without 

 reaching maturity or attaining the power of doing mischief. This destruction goes 

 on to an extent little dreamt of except by those who have minutely examined the 

 question. It is not an exaggeration, but in many cases an under-statement, to say 

 that a million germs are produced in most of the lower forms of life for one which 

 e^er reaches the reproductive stage in its turn. Numerical evidence is easily 

 obtained of this in the case of ferns and lycopodiums and fungi among plants, and 

 of many worms and fislies and other creatures of lower organization among 

 animals. This constitutes at the same time our safeguard and our danger : a 

 safeguard, by the improbability of our meeting the few sur^■ivors of this enormous 

 desti'uction ; a danger, from their rapid increase when they do happen to meet with 

 a resting-place favourable to their development. 



What is practically becoming most essential to us just now is to be able to pass 

 from vague generalities, such as these, to definite and quantitative statements. 



No doubt much may be done, and is daily being done, to come to the assistance 

 of these natural processes of purification by submitting water of doubtful quality to 

 various operations calculated either to remote certain classes of impurity, or to 

 avoid clogging or otherwise overtasking the natural or other filters. But at 

 present we are working in the dark, and empiiicaUy, in fact, applying quack 

 remedies at random, instead of setting to work systematically and intelligently. 

 Much fuller knowledge must be acquired before we can understand our business. 



In the meanwhile I think we must view with great and increasing distrust all 

 merely selective sources of water supply, and that, except perhaps in some favoured 

 localities, such as the best of the gathering grounds from which Glasgow is 

 happily supplied, we must not put too implicit confidence in any methods of 

 filtration or boring. 



Besides, then, the general investigation which I have just spoken of, there 

 remain two alternatives to consider, each of daily increasing importance in certain 

 localities. One is the separation of the drinking from the ordinary supply ; the 

 other is the distillation of the drinking-water. Neither of these are new ; and 

 there are many places where they are of ob\dous necessity, and practised with the 

 greatest care accordingly. I think both require more attention than they have 

 received in this country. 



As regards the separation of supply, it surely is not seemly that where there is 

 no scarcity of water, but only a scarcity of wholesome water, the waterclosets and 

 factories and condensers of steam engines should be put in competition with the 

 dry throats of the people for the drinkable supply. 



The question of distillation also requires further study. There seems to be 

 no doubt that by subjecting water to sufficient heat we can destroy every living 

 germ in it, and that by distillation we may combine this with the removal of 

 almost all inorganic matter. At present the process seems to be rather expensive, 

 and brings it up to a price which is far too high for its general use. But I think 

 that when the process comes to be carefully gone into, with a view to working it 

 upon a very large scale, it may not be found impossible to effect a considerable 

 saving upon this cost. In fact, the mere necessity of delivering the distilled water " 

 at as 1 w a temperature as possible, without the use of too much cooling material, 

 is a security for the employment of as little coal as possible. We should require 

 a settlement with the Excise to prevent the revenue suffering by fraud ; but no 

 doubt a compromise could be arrived at if the necessity were felt to be urgent. 



The collection and arrangement of my thoughts, with a view to the remarks 

 just addressed to you, has brought before my mind very strongly certain con- 

 siderations, some of which, being partly of a political character, I shall rather 

 indicate than discuss. 



