A^tgnst 12, iS8o] 



NATURE 



343 



would then be equidistant, which would furnish data for a 

 more exact determination of the mean temperature. 



Perhaps the most interesting part of the Report is what 

 relates to the wind which is discussed with no little ability 

 and fulness. The results establish beyond doubt that the 

 wind blows more frequently from N. and N.W. than 

 from any other directions, and that these are especially the 

 directions from which winds of high velocity come. This 

 is strikingly shown by the fact that 75 per cent, of all the 

 high winds which occurred during 1879 came from N. and 

 N.W. The N. and N.W. winds prevail from November 

 to March, and S. and S.E. winds from May to August, 

 the other months being transitional ; and with reference 

 to these S. and S.E. summer winds it is clearly shown 

 that they blow with a much less absolute velocity than do 

 the N. and N.W. winds of the winter months. 



Of almost equal importance are the facts of the rain- 

 fall. The amount for 1S79 "'-^s sS'gS inches, the rainiest 

 months being May, June, September, and October, and 

 the driest, November, December, January, July, and 

 August. The rainfall is sorted according to the direction 

 of the wind with which it fell ; and the highly interesting 

 results are arrived at that the greater number of rain- 

 storms come from N. and N.W., that the heaviest rains 

 come with N.W. winds, and that in no season are the 

 S. and S.E. winds, not even in summer when they are 

 the predominating winds, accompanied with the maximum 

 rainfall as compared with other wind-directions. The 

 rainfall partitioned in percentages according to the winds 

 with which it fell were N. 18, N.E. 9, E. 9, S.E. 5, S. 7, 

 S.W. 3, W. 17, and N.W. 32, there falling thus 67 per 

 cent, of the whole rainfall with N., N.W. , and W. winds. 



Among the changes it is proposed by Prof. Mendenhall 

 to be introduced are improved hygrometric observations, 

 which were evidently not trustworthy for 1879 ; observa- 

 tions of earth-temperatures down perhaps to a depth of 

 40 feet ; an extension of the anemometrical observations ; 

 observations of variations in the velocity of sound under 

 different meteorological conditions, the data being ob- 

 tained from the time-gun, which is fired at noon daily ; 

 and a s)'stematic investigation of the phenomena of 

 earthquakes. 



But what is urgently required in developing the meteor- 

 ology of Japan is, beyond all question, the establishment 

 of a network of stations over the Islands equipped with 

 trustworthy instruments. The sub-tropical situation of 

 Japan between the largest continent and the largest 

 ocean of the globe is, from a meteorologist's point of 

 view, unique ; and the report now under review points 

 to meteorological peculiarities in its climate of the highest 

 interest. A satisfactory statement of its climatic pecu- 

 liarities is, as our readers are aware, a desideratum ; and 

 the information which could not fail to prove of the 

 highest utility to the Japanese, and is certain to cast 

 important lights on the meteorology of Asia and the 

 Pacific, and particularly on the meteorology of this ocean 

 about latitude 33°, south to which the islands extend, can 

 be furnished from no other source than from a network 

 of meteorological stations overspreading Japan. 



MINERAL STATISTICS OF VICTORIA 

 ■pOR some years past the yield of gold in the colony 

 -•- has been steadily decreasing. In 1868 the quantity 

 of the precious metal obtained from alluvial deposits 

 amounted to 1,087,502 ounces, and from quartz-veins 

 597,416 ounces, making in all 1,684,918 ounces of gold. 

 Last year the quantities were respectively — alluvial, 

 293,310; quartz, 465,637: miking a total of 758,947 

 ounces. The comparatively rapid diminution in the 

 supply from alluvial sources is quite intelligible, as these 

 would necessarily be soonest exhausted, though it is 

 important to observe that in 1879 for the first time for 

 eleven years the return from this source shows a decided 



advance on that of the preceding year, which is attributed 

 to a better supply of water for sluicing operations, and to 

 the opening up of deep mining ground. It is to quartz- 

 mining, however, that the colony must look for the further 

 development of her gold-fields. There has been a 

 gradual decline in the yield from quartz-mines since 

 1872, when the amount obtained was 691,826 ounces. 

 But the Secretary for Mines in his recent report speaks 

 hopefully of the probable future of this important industry. 

 Up to the end of 1879 the total quantity of gold raised in 

 Victoria is estimated to have been 48,719,930 oz. 11 dwts., 

 valued at 194,879,722/. The proportion of gold in the 

 quartz varies considerably in dilferent districts. Thus, last 

 year at Castlemaine the average yield of each ton of 

 quartz was 5 dwts. 1845 grs,, while in Gippsland it 

 amounted to i oz. 2 dwts. l8'66 grs. The quartz of the 

 latter locality is by much the most auriferous in the 

 colony. The decrease in the supply of gold has been 

 accompanied by a falling off in the number of miners. 

 The men who found employment in gold mining in 1874 

 was 45,151 ; last year they numbered 37,553, which was 

 an increase, however, of 917 over the number for 1878. 

 The mining population includes an industrious and un- 

 popular contingent of Chinamen, who last year amounted 

 to 9,1 10, or 5 28 fewer than in the previous year. Taking 

 the total annual yield of gold and dividing its value 

 among the miners employed, the earnings of an alluvial 

 miner are rated last year at 48/. loj-. i\d. per annum., 

 while those of the cjuartz miners are given as 11 8/. %s. yd. 

 Deep mining in quartz reefs continues to make pro- 

 press, and the mines are becoming every year deeper. 

 Some shafts are now more than 2,000 feet deep. The 

 revenue derived by the colony from the gold districts 

 amounted last year to 15,641/. \6s. gd., being a slight 

 advance on that of 1878. 



PH YSICS I VITHO UT A PPA RATUS^ 

 II. 



AMONGST the elementary principles of mechanics 

 which are capable of easy illustration without 

 special apparatus is that of the centre of gravity. In 

 every solid mass a point can be found such that the 

 resultant of all parallel forces acting on the individual 

 particles passes through it, and such forces balance 

 themselves around this point. The gravitation-force of 

 the earth is exerted towards its centre, but this being 

 4,oco miles away, the individual forces acting on the 

 separate particles of a body on the earth's surface may 

 be regarded as parallel forces. Hence the centre of the 

 parallel gravitation-forces is termed the centre of gravity. 

 If the centre of gravity be supported, that is to say, if the 

 resultant force be met by an equal and opposite force of 

 resistance, then the body will not fall. The leaning tower 

 of Pisa does not faU because, in the first place, the 

 mortar is strong enough to bind the masonry into a sub- 

 stantial whole, and, in the second place, because the 

 obliquity of the inclination of the tower is not so great as 

 to throw the centre of gravity beyond the supporting base. 

 A vertical plumb-line dropped down from the centre of 

 gravity of the tower would meet the ground inside the 

 base. It is very easy to imitate the leaning tower by 

 taking a common wooden roller and saw-ing off a piece 

 with oblique ends. The toys which are sold under the 

 name of the Toy Blondin also illustrate the principle 

 of the centre of gravity. A metal figure slides or walks 

 down a stretched string, being kept upright by means of 

 a weight fixed to the end of the rod held in the hand of 

 the figure, thus causing the centre of gravity of the whole 

 to fall below the point of support. A simple way of 

 showing the same thing with improvised material is illus- 

 trated in Fig. 3. A couple of forks are stuck into a cork. 



■ Conlinucd from p. 322. 



