916 REPORT OF COMMISSIONER OP FISH AND FISHERIES. 



a cistern " rests upon a second cistern." The upper one (of wood or 

 otlier material) is lined with metal in such manner that a non-conduct- 

 ing substance may be inserted into the spaces " which are left at certain 

 parts between the sides of the cistern and the lining, and between its 

 floor and lining." A plate " extending along two sides of the cistern" 

 divides oft' a chamber (called the salt-chamber), and another plate on 

 the opposite sides divides off a smaller chamber (called the water-cham- 

 ber) which communicates with a central chamber by a x)ipe on the under 

 side of both. The central chamber contains " a series of guides or tubes 

 arranged alternately close on to and a little above" the bottom lining, so 

 as to cause "an upward and downward current of the cooling solution." 

 "An insulating partition on all the four sides" (composed of plates with 

 charcoal powder between them) divides off a chamber " from the space 

 or chamber immediately around the central chamber." And this sjiace 

 is occupied by the vessels which contain the water to be frozen. The 

 lower cistern contains a coil of pipes, and the overflow from the upper 

 cistern is indicated by an outlet pipe into the lower one, and surrounds 

 the coil. A pump raises the solution, as may be required, from the lower 

 cistern to a third cistern, which is mounted over a boiler, and communi- 

 cates with it by a pipe carrying a ball tap. A pipe passing from the boiler 

 is extended into a worm inside the third cistern ; it then descends and is 

 united with one end of the coil in the lower cistern 5 the other end of the 

 coil extends uj)wards " and bends over and into the water-chamber." 

 There is a discharge-tap from the boiler, and under the tap is " a crys- 

 tallizing vat." The central chamber is filled with crystallized chloride 

 of calcium. The vessels are filled with the substance to be frozen, and 

 are closed -svith insulating covers. The water-chamber is filled with 

 water, which passes into the central chamber, and i)enetrates " a con- 

 siderable mass of the crystals in passing upwards and downwards be- 

 tween the tubes or guides into the space or chamber around." The 

 solution fills this space " up to the level of the overflow of the insulating 

 partition," and passing between the vessels " descends into the narrow 

 surrounding chamber" ; when this is filled, the surplus is discharged by 

 the outlet-pipe into the lower cistern. Here the solution absorbs a fm-- 

 ther i)ortion of heat from the coil "containing condensed water from the 

 boiler." The pump raises the solution into the third cistern ; the solu- 

 tion descends, and, ha\dng "reached its proper level in the boiler," is 

 made to boil. The steam passing through the pipe and worm is con- 

 densed by contact with the solution in the third cistern ; it then descends 

 into the coil in the lower cistern, "is considerably cooled by contact 

 with the solution" in this cistern, and rises thence into the water-cham- 

 ber, "to be there almost reduced to the freezing-point previous to its 

 again entering " the central chamber. " The concentrated solution is 

 drawn from the boiler from time to time," is received into the crystal- 

 lizing vat, and is there crystalUzed in from 12 to 24 hom^s. The crystals 

 thus obtained are put into the salt-chamber "to be cooled down to nearly 



