638 PHILOSOPHICAL TRANSACTIONS. [anNO J755. 



sufficed for 4 or 5 times repeate<] pourings-in of more sea-water into the still. But 

 as a small quantity of chalk has the same good effect, and is cheaper, and more 

 easily to be had, it is therefore preferable to soap-lees. 



When there is a fire in the cook-room, the sea-water might be ready heated to 

 put into the still, without any additional expence of fuel, in the following manner : 

 about the year 17 18, Mr. Schmetou, a German gentleman, got a patent here for 

 heating great quantities of water, with little expence of fuel. Having fixed a 

 spiral iron worm-pipe, in such a brick stove or chimney as women heat their irons 

 in, thus causing the water to run from a vessel, through the worm-pipe, several 

 feet length round, in the fire. About 30 years after, Dr. H. acquainted Mr. 

 Cramond of Twickenham with this, hoping it might be of benefit in distilling sea- 

 water. On which he procured such a spiral iron worm-pipe, about 20 feet 

 long, and -^^ inch diameter; the diameter of the spiral coil was about 14 inches. 

 This Dr. H. fixed in a brick stove in his garden, with its upper end fixed to a 

 vessel, which contained 45 gallons of water. He found the event of this first 

 trial to be as follows, viz. When the water ran full bore, at the rate of a gallon in 

 17 seconds, the heat of the water was found, by a mercurial thermometer held in 

 the stream, at the lower end of the pipe, to be 80 degrees above the freezing 

 point, 180 degrees being the heat of boiling water. When, by means of a turn- 

 cock, a gallon of water was 2 miimtes in running, then the heat was 140. At 

 vyhich rate the 45 gallons would be an hour and half in running through the iron 

 pipe ; at which rate 25 gallons will run through in 50 minutes, with so consi- 

 derable a degree of heat; and if it was an hour running, the heat would approach 

 still nearer to a boiling heat, when first put into the still, which would forward 

 the distillation, if wanted. 



He pumped the heated water up again into the upper vessel ; and thus conti- 

 nued to circulate the heating water, till its heat was l6o degrees in the upper 

 vessel, viz. within 20 degrees, or -^ of boiling, the heat requisite for plentiful dis- 

 tillation. He was in hopes, that if the water in the upper vessel could have been 

 brought to a due degree of heat, and a still-head were fixed on it, with its cool- 

 ing worm-tub, then water might have been distilled in ships, by having the iron 

 worm-pipe fixed in the chimney of the cook-room : but he found, that when the 

 heat of the water in the upper vessel was 1 60 degrees ; then, in running through 

 the iron worm-pipe again, it was so over-heated as to expand in the pipe, into an 

 explosive vapour, which hindered the running of the water. However he thought 

 it not improper to give an account of this attempt, though it failed. 



Now that several effectual means are discovered, to make distillerl sea-water 

 wholesome, and also to distil it in much greater quantity in the same still, in the 

 same time, and with nearly the same quantity of fuel ; it is reasonable to believe, 

 that it will be of great benefit to navigation, not only in saving much stowage- 



