HARDWICKE'S SCIENCE-GOSSIP. 



207 



them is mainly due to absorption of their juices. If 

 there is any juice in a stone or brick wall, i.e., any 

 moisture, the ivy must have it. Besides this, the ivy 

 directly protects the wall from the wetting action of 

 raindrift. 



Frozen Milk. — The poor milkman has of late 

 been very severely handled. While the dry weather 

 of the Jubilee summer has diminished his normal cow 

 supplies, the vigilance of inspectors has deprived him 

 of his compensatory pump supplies. Science has 

 seriously interfered with commercial enterprise, by 

 supplying means for the detection of the latter. 

 Therefore it is only fair that science should give him 

 a little help now and then. It has done so lately. 

 Messrs. Kaiser, Schmeider, and Henzold, have 

 studied the changes which occur in the freezing and 

 thawing of milk, and have shown how the honest 

 milkman may unwittingly rob himself by supplying 

 some of his customers with unnaturally rich milk, and 

 then be unjustly prosecuted and fined for diluting the 

 remainder. 



The above-named experimenters found that when 

 milk is slowly and partially frozen, the ice takes 

 up the greater part of the cream, the unfrozen 

 remainder contains the casein, milk, sugar and salts, 

 but in consequence of its loss of cream appears like 

 diluted milk, and would be described as such if merely 

 tested by the ordinary lactometric instruments. Milk 

 which has been frozen should therefore be well 

 thawed and shaken up, and not sold whilst any ice is 

 visible. 



The Frost of 7th July in Belgium.— " Ciel 

 et Terre " has a long article on this subject, including 

 reports from nearly all parts of Belgium. Early in 

 the morning of July 7th, a hoar frost extended over a 

 wide area near the Eastern frontier, including the 

 following places, where covered thermometers indi- 

 cated the following minima of 'temperature, Centi- 

 grade. 



Bourg Leopold . 

 Maeseyck 

 Verviers . 

 Spa . 

 Jalhay . 

 Baraque-Michel 



dec- 

 . 2-8 

 . 4-8 

 . i-6 



-1-5 

 -i-5 



The temperature of the ground exposed freely to 

 radiation was of course much below that of a covered 

 thermometer in every instance, as the frost was one of 

 those due to excessive radiation. The latitudes of 

 Bastogne and Vielsalm where the shattered thermo- 

 meter fell l£° Centigrade below freezing are respec- 

 tively 50 and 50 20 N. latitude, the first correspond- 

 ing to the southernmost extremity of England, the 

 second to twenty miles farther south. At both places 

 the potato fields were " completely black," and the 

 young shoots of firs, laurels, dahlias, begonias, 



haricots, &c, were frozen. Similar accounts were 

 forwarded from other localities to the National Insti- 

 tute of Geography, Brussels. 



Hail on the Congo. — Something still more 

 exceptional than the Belgian frost is recorded in the 

 "Mouvement Geographique " of 27th March. It 

 occurred at " Loulouanbourg " in the country of 

 "Babouba" (query " Balonda," of Livingstone), on 

 the 13th August 1886. At about 10.30 A.M. the 

 wind turned to the east, and at midday a great 

 storm arose. At about 1 . 55 p.m. a fall of trans- 

 parent hailstones, of more than two centimetres 

 (three-quarters of an inch) in length, and half as 

 much in breadth, occurred and continued for ten 

 minutes. The lumps of clear ice were more or less 

 rectangular in shape. A heavy rain followed, and 

 the thermometer fell from 34 to 19 Cent, (from 

 109 to 66° Fahr.). The natives were terrified, 

 and declared that they had never seen the like 

 before. , 



About six or seven years ago a Russian philosopher, 

 M. Schwedoff, stated many and very cogent reasons 

 for supposing that hailstones are cosmical meteors, 

 that they come to the earth from outside our 

 atmosphere. At the meeting of the British Associa- 

 tion of 1882, Sir William Thomson ridiculed this 

 hypothesis in a very flippant and very foolish fashion. 

 He described it as a "manifest absurdity," on 

 grounds that are curiously superficial and fallacious. 

 He (Sir W. Thomson) showed that in falling through 

 our atmosphere with planetary velocity a lump of 

 ice performs 13,000 times as much work as would 

 raise an equal weight of water one degree centigrade, 

 and therefore, he asserts the ice would be melted, 

 volatilised, and dissociated into its component gases. 

 The first part of this statement may be correct. 

 In deference to Sir W. Thomson's mathematics, 

 I will assume that it is, but when we reflect on 

 the second, it is evident to anybody acquainted 

 with the rudiments of the laws of heat that the 

 "manifest absurdity" is Thomson's, not Schwedoffs. 



Everybody knows that masses of iron do fall to the 

 earth as Schwedoff supposes the ice to fall, and the 

 iron must in thus falling through our atmosphere 

 perform just as much work as the ice would. But 

 the heat calculated by Sir W. Thompson as the 

 result of this work is vastly more than sufficient to 

 fuse and volatilise the iron. How then can the iron 

 reach the earth in a solid state ? The answer to this 

 is simple enough. The work in question is done in 

 so short a time that the heat, which is all generated 

 superficially, has not time to pass through the iron, 

 and thus, as we know, the iron hailstones are fused 

 only on their surface. If this occurs with iron which 

 is a good conductor of heat, what must happen to ice 

 which is almost a non-conductor ? Clearly nothing 

 more than purely superficial fusion, evaporation and 

 dissociation. Anybody may prove this by throwing 



