350 



NA TURE 



[February 13, 1896 



miles in length by five and a half miles in width, between the 

 two main ranges of the Rocky Mountains in Colorado. As long 

 ago as 1874 it was thought that a big gold vein had been dis- 

 covered near Mount Pisgah ; and the second mining excitement 

 was in 1884 ; but during these two periods not one of the really 

 valuable ore bodies which are worked to-day was discovered. 

 Rich ore was discovered in 1890, and the rush of miners began in 

 1892. The first gold in the district was produced in the latter 

 part of 1891, and since that year the output has steadily increased, 

 being variously estimated at 5,000,000 dols. to 7,000,000 dols. 

 The ores of the Cripple Creek district are almost exclusively gold 

 ores, with seldom silver enough to be important. The gold 

 occurs both in a coarse and a fine condition, sometimes in 

 particles so small as to be invisible to the naked eye, and at 

 ther times in plates or spongy masses from an eighth to a 

 quarter of an inch in diameter. It is rarely clear and bright, 

 and is generallj' coated with a thin rusty film of a yellowish- 

 brown compound. 



A GENERAL meeting of the Members of the Federated 

 Institution of Mining Engineers will be held in Sheffield on 

 Wednesday, February 19. Arrangements have been made for 

 visits to cutlery and silverplate works and the technical schools 

 in Sheffield on February 19, and to collieries and ironworks on 

 the following day. The following papers are down for reading : 

 "The Eastern Limits of the Midland Coal-field," by Prof. Ed. 

 Hull, F.R.S. ; " Electric Welding," by Mr. T. Scott-Anderson ; 

 " The Vibromotor as applied to the Screening of Small-coal," 

 by Mr. Emerson Bainbridge, M.P. ; "The Matabele Gold- 

 fields," by Mr. F. G. Shaw ; " Photography in the Technology 

 of Explosives," by Mr. Alfred Siersch ; " Lead and Lap ot 

 Winding and other Engines," by Mr. Hargrave Walters ; " The 

 Elliott Coal-washer," by Mr. J. Piatt. 



The Comptes rendus for February contain a paper by M. 

 Maurain on the measurement of the energy dissipated in iron 

 due to hysteresis. The amount of heat generated in a sample 

 of iron when subjected to an alternating magnetic field is 

 measured by enclosing the iron inside a cylindrical glass reser- 

 voir furnished with a capillary tube. This cylinder is filled 

 with alcohol, and placed within a long magnetising coil. The 

 reservoir being carefully protected from the heat generated by 

 the passage of the current through the magnetising coil, the 

 quantity of heat developed in the iron is deduced from the 

 amount of the expansion of the alcohol. The development of 

 heat due to Foucault currents is almost entirely prevented by 

 using a bundle of very fine iron wires. The curve which gives, 

 as a function of the time, the position of the surface of the liqttid 

 in the capillary tube during an experiment, consists of a straight 

 line until the losses of heat due to radiation and conduction 

 through the walls of the reservoir become appreciable when the 

 line becomes curved. A preliminary experiment having in- 

 dicated the form of this curve ; in the final measurement care is 

 taken that the observation does not extend beyond the straight 

 part of the curve. The author finds that the quantity of heat 

 developed during one cycle diminishes as the rapidity of the 

 alternations increases. This diminution, however, becomes 

 smaller and smaller as the frequency increases, and seems 

 to be practically independent of the magnitude of the mag- 

 netising force. The author considers that the diminution 

 observed is probably due to the screening action of the outside 

 layers of the iron, and some experiments on which he is now 

 engaged seem to favour this view. 



The number of the Bulletin of Miscellaneous Information of 

 the Royal Gardens, Kew, for January, contains some interesting 

 particulars of the effects on the Gardens of the long and severe 

 frosts of the early months of 1895. These were in some respects 

 different from what might have been anticipated from previous 

 NO. 1372, VOL. 53] 



experience. Thus, while some herbaceous plants and shrubs 

 reputed to be nearly hardy have perished, the laurustinus, the bay, 

 and the arbutus escaped almost unharmed, as also did the ever- 

 green oaks. " Alpines " suffered severely, though of course the 

 cold was not so intense as the ordinary winter temperature to 

 which many of them are exposed in their native habitat ; but 

 there they are protected through the winter by a covering of 

 snow. The bamboos in the open ground were but little injured, 

 while the pampas grass was largely killed. Of our native plants, 

 the ling and the gorse were greatly damaged. Perhaps the 

 greatest destruction was among the bulbs, of which very large 

 numbers were entirely killed, especially the narcissi and 

 hyacinths. In the same journal the number of visitors to the 

 Gardens during 1895 is estimated at 1,407,369. This is about 

 30,000 more than the number for 1894, but somewhat less than 

 the average numbers for the last ten years. 



We have received from Mr. J. Eliot, F.R.S. , Meteorological 

 Reporter to the Government of India, a preliminary discussion of 

 certain oscillatory changes of pressure of long period and short 

 period in India, being part ii. vol. vi. of Indian Meteo7-ological 

 Memoirs. The author points out that the discussion of pressure 

 conditions in India requires that the observations should be of a high 

 standard of accuracy, and for many years the greatest attention 

 has been paid by the India Meteorological Department to the 

 methods of observation, and to the critical comparisf>n of the 

 data. The first part of the paper deals with the normal condi- 

 tions of pressure, and shows that the ordinary seasonal changes 

 are very regular and uniform, while the abnormal conditions, 

 such as are associated with the occurrence of storms, are, as a 

 rule, very slightly marked. The largest regular oscillation is the 

 annual change ; the readings are highest in January, and fall 

 until June, after which they rise until the end of the year. The 

 amplitude of this change is smallest in Southern India, and 

 increases with latitude. The smallness of the daily pressure 

 changes is remarkable ; only about five per cent, of the changes 

 exceed a tenth of an inch. The second part of the paper deals 

 in great detail with oscillations of pressure diff"ering from the 

 annual and diurnal changes, and which appear to be associated 

 with atmospheric movements common to the whole of Southern 

 Asia and the adjacent seas. In the long-period oscillations, the 

 transfer of air across the equatorial belt tends during one half of 

 the year to give an accumulation of air and high pressure over 

 Central and Southern Asia, whilst in the other half of the year 

 the air is drained away. The short-period oscillations are less 

 regular than either the diurnal or annual, and approximately 

 average four days in length. They appear to be common to the 

 whole Indian area, and occur almost simultaneously ; they are ap- 

 parently not due to the transmission of waves in a horizontal direc- 

 tion, but possibly to waves of rarefaction and condensation, trans- 

 mitted slowly upwards and downwards in the atmosphere, caused 

 by variations of temperature. Although the discussion is only 

 preliminary to a future paper, it teems with instructive matter 

 which will well repay careful study. 



A GOOD portrait of Lord Kelvin, reproduced by collotype, is 

 presented as a supplement to Industries and Iron of February 7. 



The newly-established Societe de Speleologie of Paris has 

 sent us the first three numbers of its quarterly journal, Spelunca. 

 Accounts of caverns in various parts of the world are gathered 

 together in the journal, several of them being illustrated by maps 

 and other figures. 



The annual report ot the New South Wales Railway Com- 

 missioners for 1894-95 — being the final one for the original term 

 of their appointment — contains, in addition to the ordinary very 

 detailed statements, a full account of the extensive alterations 

 and improvements made in the railway system since 1888. The 



