July i8, 1890.] 



SCIENCE. 



35 



circulation of cooling water. This liquid anhydrous ammonia 

 flows into the refrigerators suspended in the tank forming the 

 roof of the cooling-chamber. The pressure is then rapidly re- 

 duced by opening a communication with a separate chamber, and 

 the sudden evaporation of the liquid anhydrous ammonia takes 

 place at the expense of the sensible heat in the cold-storage bath 

 in the tank, which therefore becomes very cold, and draws heat 

 from the chamber in which the meat is stored. The bottom of 

 the tank is corrugated, which gives a large increase in the cooling 

 area; and to the lower angles of the corrugation, gutters are sus- 

 pended, carrying off the water, so that the atmosphere is dried as 

 well as cooled. On June 25, the temperature, after the doors of 

 the chamber were closed, was reduced in a comparatively short 

 time by about 40° to 39°. It was tested from the evening of June 

 14 to the morning of the 30th, and it is said that the temperature 

 of the liquid in the tank rose in that time from IGI" to 31°; the 

 fall of temperatuie in the chamber being from 53° to 36f°, while 

 in the office in which the chamber was placed the fall was from 

 65° to 61°. 



—Among the papers read at the closing meeting of the Royal 

 Society, London, was one by Professor Ewing of the Dundee Col- 

 lege, entitled "Contributions to the Molecular Theory of Induced 

 Magnetism," in which experiments of a novel and curious kind 

 were described, leading to an important conclusion. Professor 

 Ewing has examined experimentally Weber's theory of molecular 

 magnets, according to which the molecules of iron are always 

 magnets, which point anyhow in an unmagnetized piece, but are 

 turned round to point one way when the iron is magnetized. It 

 is well known that in the development of this theory by Maxwell 

 and others there has been much difficulty in reconciling the re- 

 sults of the tbeory with what is known about the magnetic quality 

 of iron and steel, and many arbitrary assumptions have been sug- 

 gested in order to make the theory fit the facts. Professor Ewing's 

 experiments have removed this difficulty, showing that no arbi- 

 trary assumptions are necessary, and that the knovvn character of 

 the magnetizing process may be deduced from the molecular 

 theory in its simplest form. The experiments, as described in 

 Nature, were made by means of a model in which a large number 

 of small pivoted permanent magnets are grouped to represent the 

 molecular structure of iron. When a magnetic field is applied, 

 the action of the small magnets on one another makes them be- 

 have in a way that exactly agrees with the observed behavior of a 

 bar of solid iron when it is magnetized. The model exhibits all 

 the variations of susceptibility which are known to take place, 

 and explains how magnetic hysteresis occurs without any thing 

 like friction among the molecules. 



— An exceptionally pretty and instructive series of new experi- 

 ments upon the action of carbon heated to whiteness in the elec- 

 tric arc on various gaseous compounds is described in a late 

 number of the Berichte by Professor Lepsius of Frankfurt, ac- 

 cording to Nature of July 3. Perhaps the most important are a 

 group of four experiments illustrating the relative combining 

 powers of the four elements, iodine, sulphur, phosphorus, and 

 carbon. The apparatus employed consists of a specially modified 

 Hofmann eudiometer, one limb of which is 40 millimetres in diam- 

 eter and 300 millimetres long, and the other longer limb narrower, 

 and furnished with a mercury reservoir at its upper end. The 

 wider limb, which is the re-action tube, is furnished with a stop- 

 cock at the top, and just below this are two tubuli through which 

 the adjustable carbon poles are inserted. At the base of the wider 

 limb a second stop cock is placed so as to permit of the adjust- 

 ment of the mercury. The gas to be experimented upon is intro- 

 duced into the apparatus at the upper stop-cock by allowing mer- 

 cury to run out at the base. Four such eudiometers are arranged 

 in a row, and 100 cubic centimetres of gas introduced into each. 

 Into the first, hydriodic acid is introduced ; into the second, sul- 

 phuretted hydrogen; into the third, phosphuretted hydrogen; and 

 into the fourth, marsh-gas. The gases thus stand at the same 

 level in each of the four re-action tubes. The current from a 

 battery whose electro-motive force should amount to 60 to 80 

 volts is then allowed to pass between the carbon poles, which are, 

 of course, in contact at first, and then gradually drawn away 



uhtU the maximum arc is obtained. Each re-action may be per- 

 formed separately, or all four may be allowed to proceed simul- 

 taneously by adopting an arrangement in multiple arc. In hydri- 

 odic acid the briUiant arc-fight is tinted a magnificent purple, and 

 the whole space above the mercury becomes filled with violet 

 vapor of iodine. Notwithstanding the considerable heating effect 

 of the discharge, the volume of gas perceptibly diminishes, the 

 liberated iodine rapidly depositing in minute crystals upon the 

 walls of the tube. So rapid, indeed, is the diminution in volume, 

 that mercury requires to be poured into the reservoir to prevent 

 the entrance of air into the re -action tube. In a very few min- 

 utes the re-action is complete, and the mercury ceases to rise. In 

 sulphuretted hydrogen the light is colored blue, and copious 

 clouds of suphur are produced, which settle upon the walls in the 

 form of a white transparent coating. The volume of gas is con- 

 siderably augmented, owing to the expansion by heat, and the 

 re-action is likewise completed in a very brief space of time. In 

 phosphuretted hydrogen the arc glows with a dazzling red light, 

 the volume visibly augments at a rapid rate, and red clouds of 

 phosphorus are thrown off, the glass walls being covered with red 

 phosphorus, among which are to be found notable quantities of 

 the ordinary yellow variety. The mercury attains its maximum 

 height in the narrow limb in a minute, at most, from the moment 

 of switching on the current. In the case of marsh gae, the white- 

 ness of the arc appears at first to be rendered more intense, and 

 is surrounded by dense black clouds of carbon, which form a 

 striking background. The upper part of the vessel, however, 

 soon becomes covered with an opaque deposit which perceptibly 

 diminishes the brilliancy of the light. The volume appears to 

 increase by leaps and bounds, and in a few seconds attains its 

 maximum. At the end of the experiment, after cooling, the vol- 

 ume of hydrogen left in the first case is 50 cubic centimetres; in 

 the second, 100; in the third, 150; and in the fourth case, 200; 

 thus showing in a most striking manner that an atom of iodine 

 combines with one atom of hydrogen, sulphur with two, phos- 

 phorus with three, and carbon with four, atoms of hydrogen. 



— According to Nature of July 3, the third summer meeting of 

 university extension and other students will be held at Oxford in 

 August next. The meeting will be divided into two parts. The 

 first part of the meeting will begin with an inaugural address by 

 Professor Max MiUler at 8.30 p.m. on Friday, Aug. 1, and will end 

 on Tuesday evening, Aug. 13. The second part of the meeting 

 will begin on Wednesday morning, Aug. 13, and end on Tuesday 

 evening, Sept. 2. This period will be devoted to quiet study. 

 The courses of lectures will be longer than those delivered during 

 the first part of the meeting, and will deal in greater detail with 

 the subjects then introduced. 



— The clove-tree was introduced into Zanzibar about the year 

 1830, and its cultivation now forms the chief industry of the 

 islands of Zanzibar and Pemba. The chief supply of cloves is 

 obtained from these islands. Consul Pratt, who has lately writ- 

 ten a report on the clove-culture of Zanzibar, says that a ten-year- 

 old plantation should produce an average of twenty pounds of 

 cloves to a tree. Trees of twenty years frequently produce up- 

 wards of one hundred pounds each. Mr. Pratt reports that the- 

 yield of the present season will probably exceed that of any pre* 

 vious season, and amount to thirteen million pounds, averaging a 

 local value of ten cents per pound. 



— A pneumatic dynamite gun built for the British Government 

 was tested at Cold Spring, N.Y., on July 8, in the presence of 

 several military and naval officei's. As the test was merely to 

 determine the range and capabilities of the gun, and not the de- 

 structiveness of the projectiles, the latter were filled with sand 

 instead of an exjilosive. Four shots were fired, two of which 

 were failures, the thin brass shells of the projectiles biursting in 

 mid-air, owing perhaps to defective packing of the sand. The 

 other shots were successful: the projectiles, weighing 520 pounds 

 each, attaining a range of 4,008 and 4,680 yards respectively, the 

 contract only requiring a range of 8,500 yards. The gun, or 

 shooting-engine as it may be called, is fifty feet long, and weighs 

 much less than four tons. It is a modification of those with 

 which the dynamite cruiser "Vesuvius'* is armed. 



