November 28, 191 2] 



NATURE 



567 



principal earthquake regions of the continent. The 

 last number of the Bulletin (vol. ii., No. 3) contains 

 the first of a series of papers on the earthquakes of 

 Haiti. In this, Mr. J. Scherer examines the distribu- 

 tion of the great shocks which have occurred since 

 the discovery of the island. He finds that their 

 central areas oscillate along three great depressed 

 zones, the more important being the northern depres- 

 sion from the Bay of Samana past Cap Haitien, and 

 the southern depression passing in a parallel direction 

 close to Port au Prince and connecting the deep ocean 

 basin to the south of San Domingo with the well- 

 known Bartlett Deep. Though these two zones are 

 separated by not more than eighty miles, it is remark- 

 able that an earthquake of the northern zone, which 

 ruins towns so completely that they have to be re- 

 built on other sites, may pass almost unfelt along the 

 southern band. 



The important problem of seasonal forecasts is 

 being attacked from various points of view. Dr. 

 Walker has applied the method of correlation in deal- 

 ing with the Indian monsoon ; Hildebrandsson has 

 discussed the influence of the "centres of action"; 

 Dr. Lockyer has considered the barometric see-saw in 

 the southern hemisphere. In a paper published in 

 1909 Dr. Arctowski discussed the sequence of the 

 variations of mean temperature and the changes from 

 year to year in the positions of relatively warm and 

 cold areas, and reached several interesting conclusions. 

 He now discusses in the Vrac Matematyczno- 

 Fizycznych, tome xxi., the corresponding changes in 

 atmospheric pressure in the United States. The re- 

 sults which he obtains do not appear to be definite 

 enough to be suitable for practical application, although 

 he states that the variations of pressure from the 

 normal can be calculated several months in advance. 

 The charts, on which his conclusions are based, are 

 given for the years 188S, 1889, 1890, 1907, and 1908 

 only, and do not appear to furnish sufficient evidence 

 either for or against his contention. He gives also a 

 table showing- that the departures from normal of 

 pressure in North America are opposite to those in 

 Iceland, but as the values are given for only thirteen 

 selected years during the period 1876-1900, the table 

 can scarcely be taken as proof of liis statement tliat the 

 see-saw is " incontestablement plus caracteristique " 

 than that found by Lockyer for Cordoba and Bombay. 



In order to determine the quantity of manganese, 

 phosphorus, silicon, or sulphur in iron or steel, a 

 certain precipitate is formed, and the weight of this 

 multiplied by a certain factor in each case wiU give 

 the percentage, if i gramme of metal is used for the 

 analysis. A simple table then, in which the weight 

 of precipitate is the argument, is all that is needed 

 to enable the analyst to read the result, and this, it 

 would be thought, any analyst would prepare for him- 

 self if he had much work of the kind to do. In order 

 to help him, however, Messrs. E. B. Atkinson and 

 Co., of Hull, have provided an instrument like a 

 large wall aneroid, with a radial index which can be 

 turned round, and behind this are arranged the figures 

 of the table. The range is limited to precipitates 

 ranging in weight from 10 to 49 milligrammes by 



NO. 2248, VOL. go] 



units. Taking, for instance, a precipitate of Mn^O^ 

 weigliing o'039 (gramme?), he will find that the 

 manganese is present in the proportion of 2'8o9 per 

 cent. It is true these figures are printed very small 

 and upside down, but they are there, and they are 

 embellished with a bevelled edge plate glass front 

 and a 9-inch back of wood stained red, and a spun 

 brass rim. The instrument is called the Ebur 

 calculator. 



A PAPER on experimental investigations of the main- 

 tenance of vibrations, by C. V. Raman, has just been 

 published as Bulletin No. 6 of the Indian Association 

 for the Cultivation of Science. This account of 

 original work is divided into six sections. Of these 

 the first deals with a new form of Melde's experiment, 

 in which, by placing the prongs of the fork inclined 

 to the string, the vibrations characteristic of the trans- 

 verse and longitudinal forms of the experiment are 

 simultaneously maintained. The two vibrations were 

 also produced at right angles to each other, and so- 

 yielded the Lissajou's figures for the octave. The 

 second section is on small motions at the nodes of a 

 vibrating string observed stroboscopically. The third 

 section treats the amplitude and phase of oscillations 

 maintained by forces of double frequency. Records 

 of the motions are obtained by a beam of light falling 

 on the string and then reflected in turn by (i) a fixed 

 mirror, and (2) a mirror fi.xed on the prong of the 

 tuning-fork. The fourth section deals with vibration 

 curves maintained by a variable spring. This is shown 

 to occur for the longitudinal form of Melde's experi- 

 ment, when the period of the force is \n times that 

 of the string, where n is any integer. The fifth 

 section is on the maintenance of compound vibrations 

 by a simple harmonic force. The possibility of this 

 follows from the previous section, and its experi- 

 mental realisation is here described. The sixth section 

 deals with transitional modes of vibration under 

 variable spring. The bulletin contains twelve illus- 

 trative plates, representing in all thirty-seven photo- 

 graphic reproductions of the curves obtained and of 

 the disposition of the apparatus employed. The whole 

 forms a welcome addition to our knowledge of such 

 vibrations and their special maintenance. 



Some remarks on the subject of photography by 

 artificial light were contributed by Mr. J. S. Dow at 

 the meeting of the Illuminating Engineering Society 

 on November 19. A number of photographs of light- 

 ing installations, some including figures of people, 

 were exhibited, and it was explained that a photo- 

 metric judgment of the "surface-brightness" of 

 objects in the field of view proved a useful method of 

 estimating the exposure. A good photograph should 

 show both the objects in the room and the sources of 

 light without halation, and this demands very careful 

 e.xposure and development. Allusion was made to the 

 difficulties of taking " snap-shots " by artificial light. 

 This seems just possible by the light of such illu- 

 minants as the Moore tube, but is at present scarcelv 

 feasible in the case of most installations using in- 

 candescent electric lamps. The introduction of a 

 very much faster plate may, however, enable even this 

 to be done. 



