Dec. 15. 1887] 



NA TURE 



167 



realizes the theoretic con litions under whiA th3 problem of 

 synchronism has beea sjlved. , This system has already been at 

 work for several years in the Ecole Polytechnique, and has been 

 applied with complete success in the Paris Observatory for the 

 synchronizing of the two clocks in the Department of Longi- 

 tudes. The problem of the distribution of time with a precision 

 approachin3^ the hundredtli part of a second is thus satisfactorily 

 solved. The apparatus is extremely simple and easily regulated, 

 and may be worked with feeble currents. — Remarks in connec- 

 tion with a work entitled " Les Ancetres de nos Animaux dans 

 les Temps geologique^," presented to the Academy by M. Albert 

 Gaudry. In this work the fossil mammals are tabulaJed in the 

 ascending order according as they appeared on the earth from 

 the Lower Miocene through all the intervening geological epochs 

 up to the present time. A concluding chap'.e." is devoted to an 

 historic survey of paleontology in the Pari; Museum. — On mag- 

 netizing by influence, by M. P. Duhem. The questions here dis- 

 cussed are : the quantity of heat liberated in the transformation 

 of a system including mag.iets, and the heat lil)erated in the 

 displacement of a magnetic mass. — New nebula; discovered at 

 the Paris Observatory, by M. G. Bigourdan. The right ascen- 

 sion and i^olar distance, with miscellaneous remarks, are given 

 of the nebuhie consecutively numbered 51 to 102. Observations 

 are appended on thirteen other nebulte previously discovered. — 

 On the division of an arc of a circle, by M. A. Pellet. The 

 approximate division of an arc in a given relation is determined 

 by means of rule and compass. — -On the expansion of compressed 

 fluids, and especially on that of water, by M. E. H. Amagat. 

 The compressibility and expansion of wate-, ordinary ether, 

 methylic, ethylic, j^ropylic, and allylic alcohols, acetone, chlor- 

 ide, bromide and iodide of ethyl, sulphide of carbon, and 

 chloride of phosphorus, have been studied between zero and 

 50°, and from the normal pressure up to 3000 atmospheres. For 

 all except water, which behaves exceptionally, the coefficient of 

 expansion diminishes with increased pressure, the decrease being 

 still very perceptible at the highest point. The coefficient of 

 water increases very rapidly at first, but afterwards diminishes 

 gradually, disappearing altogether towads 2500 atmospheres. — 

 On a new method of quantitative analysis for carbonic acid in 

 solution, by M. Leo Vignon. By the process here described 

 the presence may be detected of i cubic centimetre of carbonic 

 acid in i litre of water. — Influence of natural or superinduced 

 sleep on the activity of the respiratory combu-tions, by M. L. 

 <le Saint-Martin. It is shown that, apart from the state of fast- 

 ing, natural sleep lowers by about one-fifth the quantity of car- 

 bonic acid exhaled, and by only one-tenth the quantity of oxygen 

 absorbed ; also, tliat in sleep brought about by morphine the 

 proportion exhaled falls to one-half, and in sleep caused by 

 chloral or chloroform to (me -third, of the quantity exiialed 

 during the same lapse of time in the normal state. — On the 

 abience of microbes in the human breath, by MM. J. Straus 

 and W. Dubreuilh. These researches fully confirm the con- 

 clusions already arrived at by Lister and Tyndall regarding the 

 freedom of exhaled breath from the presence of pulmonary or 

 other microbes. 



Berlin, 



Physical Society, Nov. i i.-Prof. von Helmholtz, President, in 

 the chair. —Dr. Weinstein spoke on the determination of the elec- 

 trical re>-istance of tubes of mercury. lie employs two methods for 

 measuring the length of the tubes, one iu which the tube is com- 

 pletely filled with mercury, the other in which it is only partially 

 filled, and in which the convexity of the ends of the column of 

 mercury is taken into account. The first method is the more 

 exact, but is less simple ; the difference between the methods is 

 small. The measurement of the diameter of the tube is of great 

 importance, and is made under the assumption that the tube is 

 either a cylinder or a cone ; the latter is the more correct as- 

 sumption when the tube is long, and necessitates calibrational 

 corrections, for which Dr. Weinstein deduced the foraiulai. 

 Taking into account the want of accuracy in the constants 

 involved in the above, he considers it far better to determine the 

 volume from the heights of the capillary rise of fluids in the 

 tube. — Prof. Pictet, who was present as a guest, gave a detailed 

 account of the experiments he has made with his ice-machines, 

 which have led to results which do not agree with Carnot's 

 theories as far as the second law of thermodynamics is concerned. 

 He described the action of a perfect ice-machine, consisting 

 of a refrigerator, pump, and c )ndenser. In the refrigerator a 

 quantity of heat is taken from the salt-water bath surrounding 



it, which causes some of the fluid to evaoorate ; this vapour, at 

 the temperature of the surroundings, passes unchanged into the 

 pump, where it is compressed, and forced, at high pressure, into 

 the condenser, where it at once becomes a liquid, and gives up 

 all its heat to the surroundings. This condensed fluid then flows 

 back to the refrigerator. In a real machine of finitely small 

 dimensions, the temperature in the refrigerator falls, the vapour 

 meets with resistance in passing over into th« pu:np, and in 

 passing from the latter into the condenser, and there is a fall of 

 temperature as the heat passes out into the surroundings from 

 the liquid formed in the condenser. The speaker determined by 

 careful experiments the tension of the vapour with which he 

 worked between - 20° C. and -I- 30'' C, and then he measured 

 the temperatures in the several parts of the working machine 

 by means of manometers which registered the pressures in the 

 several parts, and from this he arrived at the result stated above. 

 The measurements were made when the pump was working both 

 rapidly and slowlj', and also when it was stopped. Prof, von 

 Helmholtz drew attention to two sources of error which cannot 

 be avoided in Prof. Pictet's experiments, and which might 

 account for the results obtained being in opposition to Carnot's 

 law. In the first place, the vapour might contain air ; this 

 would influence the pressure existing in the machine, without 

 itself undergoing any condensation, and hence it is impossible to 

 determine the temperature of the vapour accurately from mea- 

 surements of its pressure. The second source of error is, how- 

 ever, still more important. In Pictet's ice-machines, the liquid 

 used is a mixture of liquefied carbonic acid gas and sulphur 

 dioxide. From such a mixture as this the more volatile carbonic 

 acid gas must pass over into the refrigerator in larger quantities 

 than the less volatile sulphur dioxide. Hence both the vapour 

 and the liquid resulting from its condensation have a composition 

 markedly different from that of the original liquid. Now the . 

 calculations are made on the assumption that the liquid under- 

 goes no change of composition, hence the temperatures deter- 

 mined from the pressures cannot correspond to tho;e really 

 existing in the seve'al parts of the apparatus. Prof. Helmholtz 

 hence considers that the temperatures in the refrigerator and 

 condenser should be measured with thermometers, in which 

 case only it would be possible to test the truth of Carnot's 

 laws on the basis of the heat-values obtained in the experi- 

 ments. 



November 25. — Prof, von Helmholtz, President, in the 

 chair. — Dr. Stapff spoke on his measurements of the tem- 

 perature of the earth in South Africa. From his obser- 

 vations on the temperature in the St. Gothard Tunnel, and 

 a comparison of these with the temperatures observed at the 

 earth's surface, he had deduced an empirical fonnula for the 

 difference of temperature between the air and the earth : accord- 

 ing to this formula, the difference is greater the lower the tem- 

 perature of the air, and disappears when the temperature of the 

 air rises to 11° C. It hence became a matter of interest to 

 determine whether the difference is negative when the tempera- 

 ture of the air is very high. Dr. Stapff" had made use of a 

 sojourn in South Africa, near Whale Bay, while engaged in 

 geological studies, for the purpose of carrying out observations 

 on the temperature of the earth. The district in which he 

 worked lies in the Tropic of Capricorn, about in the same 

 meridian as Berlin, and the soil is sandy with a current of water 

 running beneath it towards the sea. The observations were 

 made in borings with English mining-thermometers, which were 

 allowed to remain about twelve hours at the depth where the 

 temperature was to be determined, thus insuring that they had 

 taken ujo the temperature of the surroundings. The measure- 

 ment of the temperature at the earth's surface presented very 

 great difficulties, and was only rendered possible by covering the 

 bulb of the thermometer with a layer of sand 5 cm. thick. The 

 greatest depth at which the temperature of the earth was 

 measured was 17 metres. From the determinations thus made 

 it appeared that the temperature diminished down to that depth, a 

 result undoubtedly dependent upon the fact that the measure- 

 ments were made during the hottest time of the year. The 

 speaker found that the depth down to which the temperature 

 varies with that of the air is about 13-6 metres, the temperature 

 at this depth being about 25° C. The changes in temperature 

 of the earth were very considerable, greater than those of the air, 

 amounting in the sand to some 30° to 40° C. His measurements, 

 however, did not show any negative value for the difference in 

 temperature of the air and earth. — Dr. Sieg gave an account of 

 his experiments for the determination of the capillary constants 



