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SCIENTIFIC NEVS^S. 



[Feb. 24, 18 



at such pressure as to cause its liquefaction at the tem- 

 perature of the cooling water. 



The heat rejected in the condenser is the heat of 

 vapourisation taken up in the refrigerator, less the 

 amount due to the higher pressure at which the change 

 in physical state occurs, plus the heat acquired in the 

 pump, and less the amount due to the difference between 

 the temperature at which the vapour is liquefied in the 

 condenser and that at which it entered the pump. 



With regard to the fuel required for refrigerating by 

 the ammonia compression process, it may be said that 

 with an economical boiler and engine about 240,000 

 thermal units per hour can be eliminated by the ex- 

 penditure of 100 pounds of coal per hour, with a 

 brine temperature in the refrigerator of about 20 deg. 

 Fahr. 



The application of refrigerating apparatus may roughly 

 be divided into the following heads : — (a) Ice making ; 

 (d) The cooling of liquids ; (<r) The cooling of stores and 

 rooms. 



Ice Making. — For this purpose two methods are em- 

 ployed, known as the can and cell systems respectively. 

 In the former, moulds oi tinned sheet copper, or gal- 

 vanised steel of the desired size are filled with the water 

 to be frozen, and suspended in a tank through which 

 brine cooled to a low temperature in the refrigerator is 

 circulated. The thickness of the blocks exercises an im- 

 portant influence upon the number of moulds required 

 for a given output, as a block 9 inches thick will take 

 four or five times as long to freeze solid as one of only 

 3 inches. 



Ice frozen by either of the above described methods 

 from ordinary water is more or less opaque, owing to 

 the air liberated during the freezing process, little bubbles 

 of which are caught in the ice as it forms, and in order 

 to produce transparent ice it is necessary that the water 

 should be agitated during the freezing process in such a 

 way as to permit the air bubbles to escape. The ice 

 which first forms on the sides of the moulds or cells is, 

 as a rule, sufficiently transparent even without agitation. 

 The opacity increases towards the centre, where the 

 opposing laj'ers join, and it is therefore more necessary 

 to agitate towards the end of the freezing process than at 

 the commencement. Experiments have been made from 

 time to time with the view of producing transparent ice 

 from distilled water, and so dispensing with agitation. 



Cooling of Liquids. — In breweries, distilleries, butter 

 factories, and other places where it is desired to have a 

 supply of water or brine for coohng and other purposes 

 at a comparatively low temperature, refrigerating 

 machines may be advantageously applied. In this case 

 the liquid is passed through the refrigerator and then 

 utilised in any convenient manner. 



Cooling of Rooms. — For this purpose the usual plan is 

 to employ a circulation of cold brine through rows of 

 iron piping, placed either on the ceiling, or on the walls 

 of the room to be cooled. In this, as in the other cases 

 where brine is used, it is employed merely as a medium 

 for taking up heat at one place and transferring it to the 

 ammonia in the refrigerator, the ammonia in turn com- 

 pleting the operation by giving up the heat to the cooling 

 water during liquefaction in the condenser. The brine pipes 

 cool the adjacent air, which, in consequence of its greater 

 specific gravity, descends, being replaced by warmer air, 

 which in turn becomes cold, and so the process goes on. 

 Assuming the air to be sufficiently saturated, which is 

 generally the case, some of the moisture in it is condensed 



and frozen on the surface of the pipes ; and if the air 

 is renewed in whole or in part from the outside, or if the 

 contents of the chamber are wet, the deposit of ice on the 

 pipes will in time become so thick as to necessitate its 

 being thawed off. This is accomplished by turning a 

 current of warm brine through the pipes. 



In addition to the foregoing there are, of course, many 

 other applications of ammonia refrigerating machines- 

 of a more or less special nature. Many of these are 

 embraced in the second class, cold water or brine being 

 used for the cooling of candles, the separation of paraffin,, 

 the crystallisation of salts, and for many other purposes. 

 In the same way cold brine has been used with great 

 success for freezing quicksand in the sinking of shafts, the 

 excavation being carried out and the watertight tubbing 

 or lining being put in while the material is in a solid 

 state. 



It may be added that in ammonia machines, whether 

 on the absorption or compression systems, no copper or 

 alloy of copper can be used in parts subjected to the 

 action of the ammonia. Cast or wrought iron and steel 

 may, however, be used with impunity, provided the 

 quality is good. 



IPSWICH MUSEUM LECTURES. 

 Dr. J. E. Taylor, in continuing his series of lectures upon 

 "The Romance of our Common Wild Flowers," said he 

 had already shown the wide difference existing between 

 the popular idea of a flower and the idea of the botanist. 

 The latter considered that any flower which possessed 

 stamens and pistils — practically the reproductive organs 

 — was a genuine flower. The duckweed, for instance, 

 possessed a flower of this kind, and it was indeed one of 

 the oldest flowering plants in the world, for the remains 

 of it were found in the strata deposited before the 

 Tertiary Period began. Another point upon which he 

 had insisted was that flowering was an act of expenditure,, 

 and he had now to consider the object of certain proper- 

 ties in flowers. What, for instance, was the use of the 

 perfume ? It was not quite right to say that the perfumes 

 were solely for the purpose of attracting insects. Many 

 years ago Professor Tyndall showed that perfumes had 

 the power of barring out the heat rays of the sun. 

 People in Oriental countries had made the discovery long 

 before, finding that perfumes cooled a room. In the 

 same way the smell of a flower acted as a preservative, 

 and this was the reason why, in a hot droughty summer,, 

 while the leaves became scorched and withered, the 

 more delicate petals retained a delightful freshness. The 

 halo of the perfume was a cool barrier all round and 

 about them. Upon this point the lecturer dwelt at some 

 length, refuting the narrow and ignorant theory that 

 flowers were created solely for the pleasure of humanity.. 

 In the next place it was shown that, while green flowers 

 were fertilised by the wind, which carried the pollen 

 hither and thither, most other flowers were fertilised by 

 organic agents — by birds, insects, and even by snails 

 and slugs. 



The reference to insects led to a digression, in which 

 the doctor spoke of the wonderful wisdom shown by hive- 

 bees, of the power of mimicry which some insects 

 possessed, and of the cleverness manifested by the blue- 

 bottle flies in dropping their eggs through the wire gauze 

 of the safe, so that the poor cook was utterly at a loss to 

 understand how the meat became blown. It was pointed 

 out that the tastes of insects varied exceedingly, from the 

 honey-loving instincts of the hive-bee to the carnivorous 



