NA TURE 



[February 24, 1910 



representing different kinds of fish, tapering to the tail 

 end in the form of circular or elliptic cones, and fitted 

 with fins and tails siinilar to those on the actual fishes. 

 He finds that the short conical forms are the most stable, 

 that stability is in every case secured by means of the 

 fins, and that for certain limits of velocity an elongated 

 conical form becomes unstable under the conditions existing 

 in nature. 



Many who have had experience of magnetic survey work 

 on land, but have never attempted observations at sea, 

 will be interested in an article, by Dr. L. A. Bauer, in 

 the December (1909) number of Terrestrial Magnetism and 

 Atmospheric Electricity on some problems of ocean mag- 

 netic work. It deals with the arrangements adopted on 

 board the United States survey ship Carnegie by Dr. 

 Bauer. Each of the three instrments in use is arranged 

 to determine two of the magnetic elements, and the reduc- 

 tions are made within a few minutes of the observations 

 being taken, so that if there is any disagreement repeat 

 observations may be taken at once. Recording and re- 

 ducing are in every way facilitated by the use of printed 

 forms, and results are to be published rapidly. Thus Dr. 

 Bauer intends to give a summary of the voyage ending 

 January, 1910, in the March number of Terrestrial 

 Magnetism, and future work is to be dealt with in the 

 same prompt fashion. 



We have received a separate copy of a paper on two 

 mercury manometers for small pressures, by Drs. Karl 

 Scheel and Wilhelm Heuse, of the Physikalisch-Technische 

 Reichsanstalt, which appeared recently in the Zeilschrift 

 fiir Instrumentenkundc. The first of the two manometers 

 is a slight modification of the instrument described by Lord 

 Rayleigh in 1901. A U-tube provided with a bulb on each 

 limb is filled with mercury up to the middle of the bulbs. 

 Just above each mercury surface is a fine glass point, 

 an image of which can be seen in the mercury. The tube 

 is attached to a support, which can be tilted about an axis 

 perpendicular to the plane of the tube by means of a screw, 

 while the angle of tilt is determined by the mirror and 

 scale method, the mirror being attached to the support. 

 The glass points and their images are observed through a 

 microscope. To increase the range of the instrument, in 

 the second form of it one of the bulbs can also be moved 

 up or down on the support by means of a screw, and the 

 movement measured by means of a second mirror sup- 

 ported partly on the fixed, partly on the moving, bulb. By 

 means of the two instruments the authors have determined 

 the vapour pressure of water at low temperatures to a 

 high order of accuracy. 



The existence of a negative coefficient of expansion for 

 silver iodide, first demonstrated by Fizeau, and confirmed 

 by Rodwell, has not yet been explained by any satisfactory 

 hypothesis. Grinnell Jones (Zeitschrift fiir physikalische 

 Chemie, January 25) suggests that Richard's hypothesis of 

 compressible atoms may have a bearing on this point. 

 From this point of view the volume change of a substance 

 owing to a rise of temperature is the algebraical sum of 

 the volume changes, the increase of the intramolecular 

 space owing to the increased molecular vibration, the 

 increase due to the diminution of cohesion, and a positive 

 or negative volume change owing to an alteration in the 

 mutual chemical attraction of the atoms. In the present 

 paper it is shown that the affinity of silver and iodine 

 increases with the temperature, and it is suggested that it 

 is the resulting contraction which causes the negative 

 expansion coefficient of silver iodide. 



In view of the extreme fewness of the insoluble salts of 

 sodium, exceptional interest attaches to the observations 

 NO. 2104, VOL. 82] 



of Mr. W. C. Ball, as described in the Journal of the 

 Chemical Society (December, 1909), to the effect that the 

 nitrite 5Bi(NO,),,9CsNO„,6NaN02 is substantially in- 

 soluble in water, whilst the corresponding potassium salt is 

 soluble. The use of bismuth-coesium-potassium nitrite 

 provides a reagent by means of which small amounts of 

 sodium may be detected and estimated in the presence of 

 large quantities of potassium — a great advance on the in- 

 direct methods that have usually been employed. The 

 reagent is made by dissolving 50 grams KNO, in 100 c.c. 

 of water, neutralising with nitric acid, and adding 10 grams 

 of powdered bismuth nitrate. To this liquid a 10 per cent, 

 solution of CEEsium nitrate is added until the sodium present 

 in the KNO„ has been precipitated ; the solution is then 

 filtered, and the caesium salt added to a total of 2-5 grams. 

 The method may be varied to detect caesium by the use of 

 bismuth sodium nitrite as a reagent, the precipitate having 

 the same composition as in the previous case ; rubidium 

 may also be detected, but the test is less sensitive. 



The problem of the best method of dumping stone, dirt, 

 or other spoil into water is of particular interest in Stock- 

 holm, where rock-blasting and removal is being carried out 

 continually for extensions to the harbour or to the streets. 

 We learn from a note in Engineering for February 18 that 

 a new form of automatic dumping apparatus has been 

 designed and constructed by Mr. A. F. Wiking, of Stock- 

 holm. This self-dumping barge is built with a fiush deck 

 having low bulwarks on three sides, the fourth side being 

 either left open or provided with doors which are opened 

 by the pressure of the load on deck when the barge tilts 

 over for dumping. The self-tilting of the barge is obtained 

 by forcing water, by means of compressed air, into a 

 cylindrical tank, which is carried on tripods at a height of 

 about 16 feet above the deck. The admission of water to 

 this tank upsets the stability of the barge, with the result 

 that it tilts over and discharges its load. Arrangements 

 are also provided for returning the water from the elevated 

 tank after dumping is completed, so as to enable the barge 

 to return to an even keel. 



The large ice-making plant recently set to work at 

 Grimsby by the Linde British Refrigerating Company, Ltd., 

 is described in the Engineer for February 18. The plant is 

 on the ammonia compression system, and consists of two 

 steam-driven ammonia compressors, two belt-driven treble- 

 ram water pumps, two ammonia condensers, two can ice. 

 making tanks and brine refrigerators, centrifugal brine- 

 circulating pumps, electrically driven cranes, ice crushers, 

 and elevator. There is an insulated cold store of about 

 13,000 cubic feet capacity, and an ice store capable of 

 holding 1 100 tons of ice, both stores being cooled by means 

 of pipes, through which cold brine is circulated by rotary 

 pumps. The compression plant is driven by a Morley's 

 patent cross-compound steam engine, designed to use highly 

 superheated steam, and is provided with exceptionally large 

 bearing surfaces, as it has to run six or seven months at 

 a stretch without stopping. The results of trials show 

 g'56 lb. weight of steam per indicated horse-power per hour 

 when producing 208 tons of ice per day of twenty-four 

 hours ; 5"I2 lb. of ice were made per pound weight of steam 

 The ice-making performance of the plant is about 41 tons 

 of ice per ton of coal, a very creditable performance, which 

 has not been approached by any other type of refrigerating 

 machinery. 



Messrs. Friedlander, of Berlin, have sent us copies of 

 seven catalogues of scientific publications, devoted, re- 

 spectively, to various branches of palaeontology, geography, 

 and physiography. 



