190 



NATURE 



[October 7, 1920 



of the more important ores being discussed separately. 

 An interesting chapter is devoted to the methods of 

 ore-treatment, the history of the development of the 

 so-called Colorado or Gilpin County method of gold- 

 milling being clearly traced, as also its displacement 

 by the more recent processes of cyanidation and flota- 

 tion. Justice is also done to the development of the 

 smelting process, under Mr. R. Pearce, from its 

 small beginnings at Blackhawk, removed afterwards 

 to Argo, close to Denver. Statistical tables of 

 the output are given, showing the economic import- 

 ance of this district. The remainder of the book is 

 taken up with a detailed description of all the mines 

 of importance, the geological relationships of the ore- 

 bodies being worked out in much detail. 



The Journal of the College of Science of the Im- 

 perial University of Tokyo for May lo last contains 

 an important paper, of interest to the students of the 

 genesis of mineral deposits, under the title of " A Con- 

 tribution to the Knowledge of the Cassiterite Veins of 

 Pneumato-Hydatogenetic or Hydrothermal Origin : 

 A Study of the Copper-Tin Veins of the Ak6nob6 

 District in the Province of Tajima, Japan," by Takeo 

 Kato. The district in question contains a system of 

 practically parallel veins worked at first for copper, 

 but afterwards found to contain important proportions 

 of tinstone and wolframite. The author holds that 

 " the veins of the Ak^nob^ district are all con- 

 sanguineous, and all gradations exist between the 

 copper veins containing little or no cassiterite and the 

 copper-tin veins containing much of the same 

 mineral." The veins occur chiefly in Palaeozoic slates. 

 The abnormal feature of the occurrence is the fact 

 that the district shows important exposures of in- 

 trusive dioritic rocks, forming either large masses or 

 offshoots from these. There are, it is true, dykes of 

 andesites and porphyrites, but these cut the veins 

 " and are clearly later in generation than the latter." 

 " No granitic or allied acid plutonic rocks have been 

 observed," and the author concludes definitely that 

 the veins are related genetically to the dioritic rocks — 

 an occurrence which, though common enough so far 

 as copper-bearing veins are concerned, is probably 

 unique in resf>ect of tin veins. The author's sum- 

 mary of the genesis of these veins is as follows : 

 "The copper-tin veins of the Ak6nob6 district were 

 deposited from hydrothermal solutions, still containing 

 fair quantities of mineralisers, at gradually decreasing 

 temperatures, chiefly considerably below 360° C. The 

 solutions had naturally a temperature far above the 

 critical point of water (364° C), and were gaseous 

 in character, after emanation from the consolidating 

 diorite magma. As they ascended through the sur- 

 rounding slate complex the rate of fall of the tem- 

 perature was very rapid, and they soon changed to 

 superheated hydrothermal solutions." 



The chief periods of seismic activity of the well- 

 known Comrie centre are from 1788 to 1801 and from 

 1839 to 1844. Since the latter year very few shocks 

 have been felt. Some are recorded from time to time 

 in Perrey's annual catalogues. During the last thirty 

 years five have been felt, all of them slight and dis- 

 turbing an area of at most a few square miles. Three 



NO. 2658, VOL. 106] 



of these occurred towards the close of last century \ 

 ^on July 12, 1894, July 12, 1895, and August 22, 

 1898. In the present year a slight increase of activity 

 is shown by the occurrence of a shock of intensity 3. 

 (Rossi- Forel scale) on July 21, and of a slightly 

 stronger shock (intensity 4) on September 14. 



Canad.\ is keeping well abreast of the times in 

 meteorology, and its Monthly Record of meteoro- 

 logical observations, which includes data from the 

 Colonies of Bermuda and Newfoundland, will add 

 much of value to the general knowledge of the world's 

 weather. Results for the early months of the present 

 year are to hand. Tables and maps are given showing 

 the monthly average temperature and precipitation, 

 together with differences from the normal over the 

 whole Dominion. The observations are classified for 

 province and district. For many places temperature, 

 atmospheric pressure, and humidity are given for each- 

 hour, and the mean monthly averages and totals are • 

 well set out, also the mean proportion of bright sun- 

 shine for each hour that the sun is above the horizon. 

 Observations of wind direction and velocitv and of 

 cloudiness are also obtainable. The detailed observa- 

 tions of wind both from the first- and second-class 

 stations will prove of much value to the aeronaut. 

 No observations are made at present of the form of 

 cloud, or of the direction and speed of either lower 

 or upper clouds. Such observations would be useful 

 in the elucidation of upper-air problems. 



.An analysis of the rate of ascent of pilot-balloons 

 has been made by Lieut. R. P. Batty, and is published 

 by the Meteorological Office as Professional Notes 

 No. 12. The observations were taken at Butler's 

 Cross, Salisbury Plain, from June to December, 1919. 

 The ascents w-ere not made at fixed hours of the day, 

 but when required by the School of .Artillery ; 75 per 

 cent, of the ascents were between 9h. and I3h. 

 G.M.T., and mostly during July, -August, and Sep- 

 tember. Average rates of ascent are given for each 

 of the first thirteen minutes. From 225 ascents 

 1464 minute readings were obtained, and the mean 

 rate of all ascents is 530 ft. per minute. .Ascents 

 have been grouped for sf>ecified hours of the day, and 

 the mean rate is shown to be greatest at about mid- 

 day. .Ascents are also classified according to the 

 amount of cloud in the sky, and it is seen that more 

 cloud gives an increased rate of ascent. Moderate 

 and strong winds give a higher rate of ascent than 

 light winds, and the rate of ascent for different wind 

 directions is also classified. It is noticed that imme- 

 diatelv prior to entering cloud the rate of ascent 

 almost invariably increases, mostly to 600-700 ft. per 

 minute. Rain is said to decrease the rate of ascent 

 bv about 20 per cent. The size of the pilot-balloons 

 used was 70 in. or 90 in., and their weight varied 

 from 20 to 30 grams. Tables and diagrams are given 

 showing • the variations under the different classi- 

 fications. 



Father Froc has added yet another contribution 

 to his already valuable researches on the typhoons of 

 the Far East, in the " Zi-Ka-Wei Observatory .Atlas 

 of the Tracks of 620 Typhoons, 1893-1918." The 

 atlas contains a series of charts showing the actual 



