438 



NA TURE 



[June lo, 1C09 



necessitate reference to unpublished data, are printed in 

 the report. In all these respects there is much analogy 

 between the English and German organisations. For the 

 first time an ■ appendi.\ has been added to the annual 

 report, dealing with interesting scientific matters relating 

 to weather conditions of the year and to special investiga- 

 tions. Among the latter is an article by Dr. Hellmann 

 on the window exposure of thermometers, undertaken 

 with the view of showing the small difference between 

 the older observations and those made more recently with 

 better exposure. The author points out that the window 

 exposure is still the one most generally used in Europe, 

 viz. in Scandinavia, Germany, .\ustria, Switzerland, and 

 Italy, and to some extent also in Spain and Portugal. 

 lUusfrations arc given of some of the window-screens now 

 generally in use. 



The results of meteorological and magnetical observa- 

 tions at Slonyhurst College Observatory for iqo8 have been 

 received. This observatory occupies an important position 

 in Lancashire, and its observations go back for sixty-one 

 years ; it is one of the observatories adopted by the 

 Meteorological Committee in 1867 for the supply of hourly 

 observations, and although, for financial reasons, the 

 subsidy originally allowed by the committee has had to 

 be greatly reduced, it still supplies automatic records to 

 the Meteorological Office. The year 1908 was, on the 

 whole, mild and quiet, pressure, temperature, and rainfall 

 being above the average ; the wind velocity indicated a 

 gale on four days only, the number of miles traversed 

 during the year being the smallest on record. With regard 

 to magnetic work, tabulations are supplied quarterly to 

 the Netherlands Meteorological Institute for the Inter- 

 national Committee on Terrestrial Magnetism, and con- 

 siderable time has been devoted to an examination of the 

 magnelograms of the last forty years in connection with 

 solar ' influence. The work is not complete, but the pre- 

 liminary results show many well-established recurrences of 

 disturbances at 24-hour intervals, with a maximum of fre- 

 quency between gh. and iih. p.m. (G.M.T.). The solar 

 surface has been observed on all available days ; on one 

 day only the surface was found quite free froin spots. 

 The secondary maxima of the solar activity and magnetic 

 disturbance, in 1907, is shown as follows : — 



1903 igot :qo5 1906 1907 ■ 1908 



Spot area 19 a? 68 4-8 5-8 4-6 



Declination range ... irS 119 149 I4'2 147 14-5 

 the unit of area being 1/5000 of the visible surface and 

 that of declination being one minute of arc. 



Dr. G. Agamennone contributes to the Bolletino of the 

 Italian Seismological Society, vol. xiii.. No. 2, an account 

 of the seismological service which was established in Italy 

 after the Riviera earthquake of February 23, 1S87. There 

 are now 678 observatories of the first, second, and third 

 order distributed, so far as possible, at even distances of 

 about 20 km. apart over the kingdom of Italy and in the 

 islands belonging to it, which , report regularly to the 

 central oflSce in Rome. This service, the special purpose 

 of which is to obtain a record of every earthquake which 

 takes place, enables the central office to form an estimate 

 of the extent and importance of each shock, and to issue 

 interrogatories to places not included in the network of 

 observatories when such a course seems desirable. A 

 special section of the daily weather report is devoted to a 

 brief account of the reports of earthquakes, which are 

 published more fully in the Bolletino of the Seismological 

 ^Society. Besides this organisation for the study of local 

 .rarthqu.ikcs, thirty-four observatories are equipped with 



NO. 2067, VOL. 80] i 



one or more seismographs capable of registering distant 

 earthquakes. 



Mr. Ll. T. Jones, of Bingley Grammar School, has 

 designed a simple apparatus which can be used by young 

 students to measure the diffiusion of gases. It consists 

 essentially of a L'-tube with one long and one short arm. 

 The short arm, into which gas can be passed by a side 

 tube, is closed with a piece of clay pipe-stem sealed at 

 the top. To perform an experiment the gas is first passed 

 through drying tubes and thence into the short arm of the 

 U-tube. The longer arm is then filled with mercury. 

 The gas in the shorter tube meanwhile will have been 

 forced through the porous pipe, so that the shorter arm 

 will now be full of mercury. The rate of diffusion under 

 different pressures can easily be estimated. The apparatus 

 can be procured from Messrs. W. and J. George, Ltd., of 

 Great Charles Street, Birmingham. 



Tbie Journal of the Rontgen Society for May contains 

 a well-illustrated paper, by Mr. J. H. Gardiner, on the 

 origin, history, and development of the Rontgen-ray tube. 

 The council of the society has recently got together a 

 collection of tubes showing the development of the modern 

 apparatus from the original Crookes tube used by Rontgen 

 in 1896, and has presented it to the authorities of the 

 South Kensington Museum. Several of the improvements 

 illustrated by the collection are discussed by Mr. Gardiner, 

 but the most important step taken recently appears to be 

 the substitution of tantalum for platinum in the anti- 

 kathode by Messrs. Siemens. The higher melting point 

 of tantalum makes it possible to employ currents of 

 30 milliamperes through the tube. With a well-focussed 

 lube a current of this magnitude will melt the front 

 surface of a tantalum anti-kathode i millimetre thick, 

 and Mr. Gardiner advocates the use of a magnet to 

 direct the kathode rays to a new portion of the surface. 



We have received a copy of a communication made 

 recently by Drs. Scheel and Heuse, of the Physikalisch- 

 technische Reichsanstalt at Charloltenburg, to the Zeit- 

 schrift fiir Inslruinentenkinide, dealing with the relative 

 efficiencies of many of the methods at present in use for 

 the production of high vacua. In each case a 6-litre vessel 

 of dry air was evacuated, in most cases from an initial 

 pressure of about 10 millimetres of mercury obtained by 

 a water or oil pump. A simple Toeplcr pump having a 

 vessel of 850 c.c. capacity reduced the pressure to about 

 07 of its initial value in three strokes, and took five hours 

 to redvice the pressure from o 06 millimetre to 0.00002 milli- 

 metre. A Toeplcr pump as modified by Drs. von Reden 

 and Rosenthal, requiring only 3-3 Icilograms of mercury 

 to work it, reduced the pressure from 15 millimetres to 

 000002 millimetre in a little more than two hours. A 

 Gaede pump, starting from an initial pressure of 12 milli- 

 metres obtained by a Gaede oil pump, reduced the pressure 

 to o.ooooi millimetre in an hour. The method which the 

 authors find most convenient is first to reduce the pressure 

 to about o-oi millimetre by means of a Gaede pump, and 

 to obtain further reduction by absorption of the remain- 

 ing gases by cocoa-nut charcoal cooled in liquid air. By 

 this means the pressure was reduced in less than two 

 hours from o.oi millimetre to oooooi millimetre of 

 mercury. 



Referring to the reproductions of South -African rock- 

 engravings in last week's Nature tp. 4'i). ^^'■'- ^■ 

 Lydekker writes to point out that the figure given as a 

 buffalo is misnamed, the animal represented being an 

 eland. 



