October 3, 1907] 



NA TURE 



579 



An interesting report on tlie borax deposit of Lal^e 

 Salinas, Peru, lias been published by Mr. A. Joiliamowilz 

 (Boletin del Cucrpo de Ingenieros dc Miiuis del Pern, 

 Xo. 49). The so-called lake is dry for thr },'rfatpr part 

 of the year, and the borax deposit is about 3 feet in 

 thickness. It consists of ulexite, containing 30 per cent, 

 of boric acid. The bed is impermeable, so that water 

 cannot reach the lake at places where borate occurs. The 

 borate is extracted by means of shallow pits, which become 

 lillcd with water when the borate is removed. Reports 

 liavc also been issued by Mr. W. Turner and .Mr. J. J. 

 Bravo on the geology of the River Chillon (Boletin 

 \o. 48), and by Mr. H. C. Hurd on the w.uer supply of 

 <he valley of l.amb.iyeque (Boletin No. 47). 



The current issue of the Proceedings of the .American 

 Pliilosophical Society (vol. xlvi.. No. 1R5) covers two 

 hundred pages, and contains seventeen papers of very 

 varied interest. The most important memoir is a detailed 

 account of the geology of the San Francisco peninsula, by 

 Mr. Roderic Crandall. It describes the Montara granite, 

 the Franciscan series, the Merced series (Pliocene), the 

 Pleistocene beds, the serpentines, the igneous intrusive 

 rocks, and the schists represented on the peninsula. The 

 age and origin of the rocks are discussed, and an excellent 

 coloured geological map is appended. Another paper of 

 great interest is that by Mr. E. B. Titchener and Mr. 

 \V. H. Pyle on the effect of imperceptible shadows on the 

 judgment of distance. Careful experiments show that such 

 shadows, raised almost to the limit of perceptibility, exert 

 no influence irpon the judgments of distance by five 

 observers. Mr. M. D. Kuell gives the results of a pre- 

 liminary study of some modern micrometers. Me collected 

 a number of stage micrometers, and measured five to ten 

 spaces on each with great care. The results show that no 

 advance in precision has been made during the last twenty- 

 five years. Indeed, the results do not seem to equal those 

 of the former period. The papers of chemical interest deal 

 wilh the measurement of the action of water on metals, 

 (he production of synthetic alcohol, and the association 

 theory of solutions. 



TirE September number of Symons's Meteorological 

 Magazine contains a useful paper by Mr. R. 11. Curtis 

 on the distribution of bright sunshine over the British 

 Isles. Two forms of recorder have been in general use, 

 the photographic and burning instruments ; their records 

 frequently differ considerably, and not always in the same 

 direction. For the sake of uniformity, the Meteorological 

 Office now only publishes records from the burning instru- 

 ment, and these alone have been used in Mr. Curtis's dis- 

 cussion. Latitude being an important factor, we naturally 

 find that the sunniest parts of the United Kingdom are 

 the most southern, the annual total of hours' duration 

 decreasing from igoo hours in the Channel Islands to 

 1200 over the north of Scotland. A very clear map shows, 

 however, that the lines of equal duration have a strong 

 tendency to follow the coast lines both in east and west, 

 and that a large portion of the central area of England 

 and of the south-west of .Scotland is adversely influenced 

 by smoke and dust ; in winter the largest totals of sun- 

 shine are obtained in the south-west. A great part of 

 Ireland, central Wales, and the Highlands of Scotland are 

 still very inadequately represented by sunshine recorders. 



September has proved an exceptionally fine and dry 

 month over the entire kingdom, and in England the 

 period without rain continued for about three weeks. Of 

 the stations reporting to the Meteorological Office, the 

 least measurement of rain for the month was 0'28 inch at 

 NO. 1979, VOL. 76J 



Yarmouth, which is only 12 per cent, of the average, whilst 

 at Bath the percentage was 18, and at Liverpool 19. .At 

 many places in different parts of the kingdom there was 

 less than 50 per cent, of the average. In London the 

 aggregate measurement was a-^S inch, which is 28 per 

 cent, of the normal. The total measurement of rain since 

 the commencement of the vear is deficient, except in the 

 extreme north and west. In London the deficiency 

 amounts to 4'88 inches, and, so far, .April is the only 

 month with an excess of rain ; the greatest deficiency in 

 any month is 1-48 inches, in September. The duration 

 of sunshine so far this year is, in London, fourteen hours 

 more than the average, the excess occurring in January, 

 February, March, and September. There were in all 

 during the six summer months from April to September 

 sixty-one days at Greenwich with the temperature 70° 

 and above, and only two days with a temperature of 80°. 

 The only years since 1841 with fewer days of 80° and 

 above are i860, when the thermometer did not once touch 

 80°, and 1862 and 1879, when there was only one instance 

 of so high a temperature. The type of weather which 

 prevailed with such persistence throughout September has 

 now complrtelv changed, and wilh October rains have 

 become general. 



.A SUMMARY of the paper on the effects of heavy pressures 

 on arc spectra, communicated by Mr. W. J. Humphreys 

 to the American Physical Society, appears in the Physical 

 Review for June. Pressure seems to increase the width 

 of all lines and displace most of them towards the red by 

 amounts approximately proportional to the pressure. The 

 extent of the shift varies from line to line, and is prac- 

 tically independent of the amount of material used. The 

 intensities of some lines are increased, of others decreased. 

 by the pressure. 



Mr. E. F. Nortiirup directs attention in the Physical 

 Review for June to the magnitude of the forces exerted 

 by the parts of a non-electrolytic liquid carrying an electric 

 current on each other, and describes several striking ex- 

 periments in illustration. One of these consists in sending 

 a large current through a narrow channel of mercury 

 connecting two small reservoirs of mercury. With a 

 current of 800 amperes a V-shaped depression half an 

 inch deep formed at the centre of the channel, the mercury 

 flowing into the reservoirs. .A slight increase of the 

 current broke the continuity of the mercury in the channel. 

 On the liquid flowing together again the circuit was re- 

 made, the arrangement thus constituting a slow and 

 irregular interrupter. 



In the Physikalische Zeilsclirift for September 15 Dr. 

 K. E. F. Schmidt has an article on the " barretter," i.e. 

 the bolometer when used to detect and measure rapid 

 electrical oscillations. He shows that by enclosing the in- 

 strument in an oil bath the necessity for using two similar 

 instruments is obviated. The " barretter " in series with 

 a galvanometer of low . resistance forms one arm of a 

 resistance bridge, the other arms of which are wound so 

 as to have considerable inductance, and thus confine the 

 oscillating current to the "barretter," the terminals of 

 which are connected to the circuit in which the oscillations 

 are to be measured. The oscillating current heats the 

 fine wire of the instrument, and thus disturbs the balance 

 of the bridge by a measurable amount. The conditions 

 for maximum sensitiveness are considered by Dr. Schmidt, 

 and the results expressed in the form of curves. 



Under the title " Grandeur ct D<;cadence des Rayons-N : 

 Histoire d'unc Crovance," M. Henri Pi^ron gives in the 



