WATER, SEA 1103 



Experiments undertaken with a view' to determine the amount of these gases pre- 

 sent in water, showed that this amount varied with the state of purity of the water ; 

 that whilst ordinary rain-water contains, on an average, 15 cubic inches of oxygenised 

 air per gallon, it was constituted as follows : 



Carbonic acid 6'26 



Oxygen 5'04 



Nitrogen 370 



15-00 



Sea water, owing to the various substances which it holds in solution, contains only 

 on an average 5 cubic inches of gases, more than one-half of which is carbonic acid ; 

 or, in other words, 1 gallon of sea water contains about two-thirds less gases than 

 ordinary rain-water, and one-half less gases than river water. 



It has been ascertained that air begins to be expelled from such natural waters 

 when the temperature reaches about 130 Fahr. ; and wo know that when the tem- 

 perature reaches 212 Fahr., all the air which it contained has been expelled, and it 

 is for this reason that distilled water contains no air. 



The apparatus invented by Dr. Normandy is represented in figs, 2100, 2101. It 

 consists of three principal parts an evaporator, a condenser, and a refrigerator 

 joined so as to form one compact and solid mass, screwed and bolted, without sol- 

 dering or brazing of any kind. The evaporator is a cylinder, partly filled with sea 

 water, into which a sheaf of pipes is immersed, so that on admitting steam at a cer- 

 tain pressure into these pipes it is condensed into fresh, though non-aerated water by 

 the sea water by which the pipes are surrounded, that sea water being thus heated and 

 a portion of it evaporated at the same time ; for it is one of the properties of steam to 

 be condensed by water, no matter how high the temperature of that water may be, if 

 it be only inferior to that of the steam. This non-aerated water becomes aerated, as 

 will be explained below. On board steamers, the steam is obtained directly from 

 the boilers of the shfp ; in sailing-vessels it is procured from a small boiler which 

 may, or may not be connected with the hearth, galley, or caboose. 



The steam at a pressure being, of course, hotter than ordinary boiling water, serves 

 to convert a portion of the water contained in the evaporator into ordinary or non- 

 pressure steam, which, as it reaches the pipes in the condenser, B, is resolved into fresh 

 aerated water. By thus evaporating water under slight pressure, one fire performs 

 double duty, and thus the first condition, that of economy, is completely fulfilled, for 

 while, in the usual way, 1 Ib. of coal evaporates at most 6 or 7 Ibs. of water, the same 

 quantity of coals, put under the same boiler, but in connection with this apparatus, is 

 thus made to evaporate 12 or 14 Ibs. of water ; or, in other words, from the same amount 

 of coals or of steam employed, the machine which is described will produce double the 

 quantity of fresh water that can be obtained by simple or ordinary distillation ; that 

 is to say, double the quantity obtained by the ordinary condensers. 



The comparative trials made in 1859 on board H.M. ships the Sphynx, Erebus, 

 and Odin, at Portsmouth, before the Commissioners of the Admiralty, most con- 

 clusively proved the perfect accuracy of that statement. 



The steam issuing from the evaporator, and which is condensed by the water in 

 the condenser, imparts, of course, its heat to the sea water in it ; and as this water is 

 admitted cold at the bottom, whilst the steam of the evaporator is admitted at the top 

 of the condenser, the water therein becomes hotter and hotter gradually as it ascends, 

 and when it finally reaches the top its temperature is about 208 Fahr. 



It has been already stated that water begins to part with its air at a temperature of 

 about 130 Fahr., therefore the greater portion of the air contained in the water 

 which flows constantly and uninterruptedly through the condenser is thus separated, 

 and led through a pipe into the empty space left for steam -room within the evaporator, 

 where it mixes with the steam. 



Now, as about six gallons of sea water must be discharged for every gallon of fresh 

 water which is condensed, and as each gallon of sea water contains, as was said before, 

 5 cubic inches of air, and whereas the utmost quantity of it that fresh water can 

 naturally absorb is 1 5 cubic inches per gallon, it follows that the steam in the evapo- 

 rator, before it is finally condensed, has been in contact with twice as much air as 

 water can take up, the result being a production of fresh water to the maximum of 

 aeration, that is, containing as much air as in pure rain-water. 



This aeration of the water to the maximum and with the air naturally contained 

 in the water in its original state, though a condition of the utmost importance, Dr. 

 Normandy having failed in removing the odour and taste in question, it became neces- 

 sary to try to discover whence came that flavour which no aeration could destroy, 

 except after a considerable length of time, and even then never perfectly. That water 



