SCIENCE- G OSSIP. 



349 



CONTRIBUTED BY W. H. CADMAN. 



Lord Kelvin. — We are glad to notice the name 

 of this great physicist included in the modest list 

 of nine distinguished men upon whom the young 

 University of Wales will confer in May the degree 

 of Doctor in Legibus (honoris causa), in celebrating 

 the second installation of a Eoyal Chancellor. 



Effect of Smoke and Gas upon Vegeta- 

 tion. — The extent of injury to agricultural and 

 forestry interests by pollution of the atmosphere 

 in cokeing and other manufacturing operations 

 has received considerable attention during the last 

 few years. W. A. Buckhout has recently noted 

 the condition of vegetation in the immediate 

 vicinity of a number of manufacturing centres in 

 America. The injurious effect of the gases, 

 smoke, and soot is shown by the destruction of 

 forests and orchards in the vicinity of large manu- 

 facturing establishments. The most- practicable 

 method for the prevention of some of this injury is 

 believed to be the erection of tall smoke stacks or 

 chimneys, in order to secure the most effectual aid 

 in rapid dilution of the gases. Much mischief 

 would be prevented if such works were erected in 

 large open plains instead of in valleys, as is so 

 often the case. 



Influence of Mountains on Hailstorms. — 

 This disputed subject has received much attention 

 at the hands of the Italian Meteorological Office. 

 In the last publication Professor V. Monti compares 

 the results of observations for seven years at the 

 typical stations, the Collegio Eomano, and Monte- 

 cavo, an isolated station at an altitude of 1,000 

 metres, near Rome. Eighty days of hail were 

 observed at Montecavo against forty-one at Rome. 

 During the same period there were 176 thunder- 

 storms at Rome, compared with 129 at the other 

 station. The excess of hail at the mountain 

 station does not appear to be attributable to a 

 greater intensity of atmospheric electricity. The 

 monthly mean temperature at Rome is about 10° C. 

 higher than at Montecavo, and hence Professor 

 Monti suggests that the fusion of hail in crossing 

 the warmer stratum of air may account for the 

 smaller amount at the lower station. 



Mathematical Investigation of Intel- 

 lectual Ability.— The "Proceedings of the 

 Royal Society," No. 456, March 7th, 1902, contain 

 an amusing article on " The Correlation of Intel- 

 lectual Ability with the Size and Shape of the 

 Head," drawn up by Karl Pearson, F.R.S. Miss 

 M. Beeton, of Girton College, pi-epared cards 

 giving the name, college, and chief physical 

 measurements of upwards of a thousand Cam- 

 bridge undergraduates. The nature of the degrees 

 ■ultimately obtained by them were then compared 

 with these measurements. Tables are given show- 

 ing the relation between ability and length and 

 breadth of the heads of different men. The 

 author finally concludes that " very brilliant men 



may possibly have a very slightly larger head 

 than their fellows ; but, taking the general popu- 

 lation, there is really a very insignificant associa- 

 tion between size of head and ability. For 

 practical purposes it seems impossible to pass any 

 judgment from size of head to ability, or vice 

 versa." 



Rate of Recombination of Ions in Gases 

 UNDER Different Pressures. — "The London, 

 Edinburgh, and Dublin Phil. Mag." for March 

 1902 contains an interesting paper on this subject 

 by R. K. McClung, M.A. Any gas which has been 

 exposed to Rontgen rays retains the ionisation 

 thus produced for a short time after the source of 

 radiation has been removed. The negative and 

 positive ions take an appreciable time to recom- 

 bine with each other. This question of the rate 

 of recombination of ions was investigated by Pro- 

 fessor Rutherford for air and some other gases at 

 atmospheric pressure. McClung undertook his 

 research to find the relation between the rates of 

 recombination at dift'erent pressures. The rays 

 from an X-ray bulb passed through a brass cylinder 

 containing the electrodes consisting of thin 

 aluminium foil between which the leak was mea- 

 sured. The cylinder was made so that it might 

 be exhausted or subjected to considerable internal 

 pressure as desired. The results obtained show 

 that the rate at which the ions recombine in 

 ionised air is determined by the same law, no matter 



what the pressure may be — namely, -- = —a.'n}, 



where n is the number of ions per c.c. in the gas 

 at any time, t, after the rays have ceased, and o is a 

 constant for any given gas. The same law was 

 found to hold true for hydrogen and carbon 

 dioxide as for air. 



Electric Detonators. — It is not, perhaps, 

 generally understood how useless dynamite and 

 other high explosives would be except for the 

 insignificant little detonator. A ton of dynamite 

 may lie secure, yet the smallest Nobel detonator 

 exploded in the mass sets free the terrible resist- 

 less power of the dynamite in all its fury. 

 Detonators consist of thin copper tubes closed at 

 one end and filled with a detonating composition 

 consisting of fulminate of mercury and, generally, 

 potassium chlorate. Fulminate of mercuiy is pro- 

 duced by the action of nitric acid and alcohol 

 upon mercury. It is very sensitive to heat and 

 shock, and, being one of the quickest explosives 

 known, gives an extremely sharp shock, which is 

 exactly what is required to detonate dynamite. 

 Electric detonators usually contain a mixture of 

 antimony sulphide and potassium chlorate as a 

 priming mixture, in addition to the fulminate of 

 mercury. There are two systems of electrical 

 blasting — namely, high tension and low tension. 

 The high-tension E.D. fuses are largely used in 

 Europe. Attached to the ends of the wires em- 

 bedded in the detonator is a sensitive chemical 

 composition which is ignited by a spark passing 

 between the terminals, resulting in an explosion. 

 Low-tension E.D. fuses have within the detonator 

 a fine platinum wire encased in a suitable flashing 

 mixture ; and this wire on becoming heated by the 

 current ignites the mixture, which in its turn 

 explodes the detonator. This system is in almost 

 universal use in tropical countries. The low-ten- 

 sion possess a great advantage over high-tension 

 fuses, in that their efficiency can be tested at any 

 time with a galvanometer. 



