ioS 



HARDWICKE'S SCIENCE-GOSSIP. 



some speculative mathematicians who have "proved" 

 (to their own satisfaction) that the earth is solid 

 throughout. But the intellectual machinery used by 

 these gentlemen is so powerful that an expert in its 

 use can demonstrate anything his imagination may 

 suggest whether true or false, reasonable or absurd. 

 The question whether the increase of temperature 

 which experiment has proved to proceed as we 

 descend below the surface of the earth will continue 

 similarly at still greater depths than we have yet 

 attained, is a physical one to be proved or disproved 

 by direct physical experiment. Everything that is at 

 present known indicates the existence of a store of 

 calorific energy, which, so far as human demand is 

 concerned, is practically inexhaustible. We have but 

 to tap it effectually and draw perennial supplies. 

 Whether we shall avail ourselves of it or not will be 

 determined simply by the cost of reaching it as 

 compared with the cost of raising coal. The thick- 

 ness of the earth's crust is better studied by observing 

 Its own movements directly (as in earthquake- waves), 

 than by making complex calculations concerning the 

 supposed astronomical influences of internal earth- 

 tides. 



Flies as Sanitary Inspectors. — My own ex- 

 perience and that of many friends concur in the 

 conclusion that house-flies have been unusually abun- 

 dant and vicious this summer. The reason is not 

 very evident, unless it be that the short spell of hot 

 weather we had earlier in the summer than usua' 

 brought them forth unusually. Having muttered 

 many terrible denunciations of these disturbers of 

 afternoon naps, my conscience insists on making 

 amends by quoting a curious fact recorded in " The 

 Sanitarian." Offensive odours were observed in a 

 house in an American city, but their source could not 

 he detected. The carpet of the offending room was 

 raised, and a carpenter engaged to take up the floor, 

 when it was suggested that the usual sanitary inspector 

 should be superseded by a cheaper rival. Two 

 bluebottles were brought from a neighbouring stable, 

 and the doors and windows of the room closed. The 

 flies proceeded to one of the spaces between the 

 flooring boards, and on raising the floor at this part 

 the remains of a dead rat in an active stage of 

 decomposition were there discovered. 



Flies have been accused of carrying infection by 

 alighting on decomposing matter, and proceeding 

 from thence to sugar basins, &c, but I am not aware 

 that any direct experiments have been made on this 

 subject. Their remarkable care in brushing them- 

 selves throws doubt on it. I have especially observed 

 their proceedings in cleaning their feet by rubbing 

 them against each other with a twisting or coiling 

 action that must be very effective. 



Nitrogenous Compounds in Rain-Water.— 

 We are always taking nitrates out of the soil wherever 



it is cultivated and crops are reaped, and besides this 

 the rains wash such easily soluble salts down to the 

 rivers and thence to the sea. The question of how 

 these are perennially renewed has long been discussed. 

 Messrs. Berthelot and Andre have taken up the 

 subject again ("Comptes Rendus," vol. 102, p. 957), 

 and state that rain-water not only contains nitrogen in 

 the form of ammonia, and in nitrates and nitrites, but 

 also in the form of soluble organic compounds, which 

 are not decomposed by boiling with alkalies, and in 

 insoluble nitrogenous particles derived from the air. 

 In analysing rain-water it is essential to estimate all 

 the four quantities, and this should be done im- 

 mediately after the fall of the rain, which should not 

 be allowed to stand in the collecting apparatus for 

 any considerable length of time, as opportunity would 

 thus be given for the development of organisms 

 derived from the air. 



I should add in explanation, that the nitrogen so 

 abundant .as a constituent of atmospheric matter is 

 curiously inert in its uncombined condition, and tha t 

 one of the theories of the origin of nitrogenous com- 

 pounds is that electrical discharges in the midst of this 

 inert nitrogen and aqueous vapour effects the combina- 

 tion of nitrogen and hydrogen, i.e. the formation of 

 ammonia ; and from this, as a starting point, the 

 formation of the nitrates, nitrites and their salts, is 

 explained, as below. 



Nitrification. — Until a comparatively recent 

 period the mode in which nitrogenous organic matters 

 are onidized in the soil and converted into nitrates 

 and nitrites, has presented a chemical puzzle. It is 

 now solved in a fairly satisfactory manner. It appears 

 to be due to the action of microbia, such as bacteria 

 and other microscopic organisms that assimilate these 

 organic compounds, and excrete them as nitrates and 

 nitrites of the alkaline and earthy bases, and also of 

 ammonia. These ammoniacal and other compounds 

 thus formed supply food to the visible vegetation ; are 

 important natural manures. Thus the sewage of 

 towns may become the food of microbia, the excre- 

 tions and dead bodies of these the food of plants, and 

 these plants the food of man, either directly as 

 vegetables, or as the flesh of animals that have fed 

 upon the vegetables. 



Ensilage Compared with Hay. — Experiments 

 with ensilage are still proceeding. L. Broekema and 

 A. Mayer compared the yield of milk from two sets 

 of cows, one fed for a definite period with hay, the 

 other with sour ensilage from the same grass as the 

 hay. These foods appeared to produce equal quantities 

 of milk, but the fat in the milk of the ensilage-fed 

 cows exceeded that in the milk of the hay-fed 

 cows by 0*3 per cent., the other constituents remain- 

 ing the same. The cows fed with ensilage lost 

 weight. 



From these and other experiments it appears that 



