1102 WATER, SEA 



tion to convert it into fresh water, and that the solution of the problem is altogether 

 dependent upon a still constructed so as to produce, by evaporation, a great quantity 

 of distilled water, with a consumption of fuel sufficiently small to become practicable. 



Distillation at a cheap rate is doubtless an important item, and fuel being a cum- 

 brous and expensive article on board ship, it is superabundantly evident that, sup- 

 posing all the apparatus which have hitherto been contrived for the purpose to answer 

 equally well, that one would clearly merit the preference which would produce most 

 at least cost ; but there are, besides, other desiderata of a no less primary importance, 

 and it is from having neglected, ignored, or been unable to realise them, that all the 

 apparatus for obtaining fresh water from sea water, which have been from time to 

 time brought before the public, have hitherto, without exception, proved total 

 failures, or, after trial, have been quite discarded, or fulfil the object in view in a 

 way so imperfect or precarious, that, practically speaking, the manufacture of fresh 

 water at sea, or from sea water, may be said to have been, until quite lately, an un- 

 accomplished feat. In order to understand the nature of the difficulties which stood 

 in the way of success, a few words of explanation become necessary. 



When ordinary water, whether fresh or salt, is submitted to distillation, the con- 

 densed steam, instead of being, as might be supposed, pure, tasteless, and odourless, 

 yields on the contrary a liquid free from salt, it is true, but of an intolerably nauseous 

 and empyreumatic taste and odour which it retains for many weeks ; it is, moreover, 

 insipid, flat, and vapid, owing to its want of oxygen and carbonic acid, which water 

 in its natural state possesses, and of which it has been deprived by the process of 

 distillation. In the absence of ordinary fresh water, this distilled water, however dis- 

 agreeable and objectionable it may be, is of course of use so far as it is fresh, but the 

 crews invariably refuse it as long as they can obtain a supply from natural sources. 



With a view to remedy the defects just alluded to, various means have from time to 

 time been proposed and employed : such as the addition of alum, sulphuric and other 

 acids, chloride of lime, &c. ; but it is evident that chemical reagents cannot effect the 

 object ; but if even they did, their use is always unsafe, for their continuous and daily 

 absorption might, and doubtless would, cause accidents of a more or less serious 

 nature, not to speak of the trouble and care required in making such additions. 

 Liebig said, with both authority and reason, that, as a general rule, the use of chemicals 

 should never be recommended for culinary (or food) purposes ; for chemicals are 

 seldom met with in commerce in a state of purity, and are frequently contaminated 

 by poisonous substances. On the other hand, the percolation through perforated 

 barrels or coarse sieves, porous substances, plaster, chalk, sand, &c., the pumps, 

 ventilators, bellows, agitators, which have been proposed to aerate the distilled water 

 obtained, and render it palatable, are slow in their action, of a difficult, inconvenient, 

 or impossible application ; and as to leaving the distilled water to become aerated by 

 the agitation imparted to it in tanks or casks by the motion of the ship, this must be 

 continued for a length of time, proportioned of course to the -vigour of the oscillations 

 imparted to the ship by the violence of the waves, and the time thus required is 

 alwaj'S considerable ; yet in this way, and finally by pouring the water several times 

 from one glass to another before drinking it, it may become fully aerated, but without 

 entirely losing its vapid and nauseous taste and odour. 



But before proceeding further, it may not be amiss to say a few words respecting 

 another condition in the construction of marine condensing machines, which, from not 

 being sufficiently taken into account, frequently puts them suddenly out of service, or 

 necessitates constant repairs. 



The question which had hitherto been left unanswered, and yet which nuist be in- 

 tegrally solved before success could be hoped for, is the following: 



To obtain, with a small proportion of fuel, large quantities of fresh, inodorous, 

 salubrious, aerated water, without the help of chemical reagents, by means of a self- 

 acting and compact apparatus capable of being worked at all hours, under all latitudes, 

 in all weathers and conditions compatible with the existence of the ship itself, and 

 incapable of becoming incrusted, or of otherwise going out of order. 



How this complex and difficult problem was solved by Dr. Normandy we now pro- 

 ceed to explain : 



It is a known property of steam that it becomes condensed into water again, 

 whenever it comes in contact with water at a temperature lower than itself, no matter 

 how high the temperature of that condensing water may be. 



It is known that the sea and other natural waters are saturated with air containing 

 a larger proportion of oxygen and of carbonic acid than the air we breathe. In effect, 

 100 volumes of the air held in solution in water contain from 32 to 33 volumes of 

 oxygen, whereas 100 volumes of ordinary atmospheric air contain only 24 volumes of 

 oxygen. Again, ordinary atmospheric air contains only 5^5 of carbonic acid, whereas 

 the air held in solution in water contains from 40 to 42 per cent, of carbonic acid. 



