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NATURE 



\June 15, 1882 



its distance from its armature, is least, the greatest possible por- 

 tion of the work being thus put upon the clockwork, and the 

 least upon the battery. 



This spring aids the electro-magnet, but does not in any- 

 wise reduce the effect of the reversing spring in holding the 

 clutch to its work ; so long as the base of that spring is un- 

 moved, its action is unimpaired. The resistance of these 

 springs occurs only during the ascent of the needle-bar, which is, 

 therefore, counterpoised to excess, and the resistance and the 

 motion are thus rendered uniform. By reason of the form of 

 the clutch-teeth before described, there is no outward thrust upon 

 the clutches while in action, and hence the reversing spring 

 requires only to be strong enough to throw the arm over and 

 to shift the clutches. The stop of the clutch-arm next the 

 electro-magnet is an insulated plate, to which the battery-wire 

 leading from the magnet is connected, so that as soon as the arm 

 has left the stop the circuit is again broken, although the needle 

 may for a short time remain in contact with the mercury ; the 

 recording-point is at once withdrawn, and thus makes upon the 

 paper a single perforation which must be a true record of the 

 position of the mercury in the tube, uuafTected by friction or 

 other disturbing cause, since this action must always take place 

 at the moment of contact of the needle with the mercury, and 

 these dots or perforations are repeated at the end of each interval 

 of time required for the needle-bar to ascend and descend the 

 required distance, which will be about two minutes with the 

 wheel-motion designated. 



The graduation of the scale upon the paper must correspond 

 with the movement of the mercury in the tube of the thermo- 

 meter as accurately as the graduation of the scale of an ordinary 

 thermometer corresponds with the movement of the mercury in 

 its tube. 



If but one instrument of this sort is to be made this is very 

 easy, the rate of motion is a cerlained, a scale is made to fit it, 

 and the paper is ruled to that scale. 



In all thermometers heretofore made the scale has been made 

 to fit the tube, but if more than one of these instruments i- to 

 be made, it becomes necessary, or at lea-t very convenient, to 

 have one set of ruled paper- that will fit all the instruments, and 

 it then becomes necessary to reverse the practice and to make 

 the tubes to fit the scale. 



The rise and fall of mercury in a thermometer depends upon 

 the proportion between the diameter of the tube and the volume 

 of mercury in the tube and bulb, and while it is possible to con- 

 struct these parts in such proportion as to obtain proximately a 

 given motion, it is not possible thus to obtain it exactly. 



The tube and bulb are made in separate parts, as show n in Fig. 

 I, of such size that when the tube is thrust half way into the 

 bulb, the volume of mercury filling the tube half way at 32 

 Fahrenheit is as nearly as may be properly proportioned to the 

 diameter of the tube. If now there be found too much motion, 

 the capacity of jhe bulb is diminished by thrusting the lube 

 further in, ami vice versa, and the proper height of mercury at 

 32° for that purpose is marked upon the tube. 



Mercury exposed to the air will slowly form a coating of oxide 

 upon its surface. To prevent thi-, a small quantity of glycerin 

 or of oil free from oxygen is placed in the thermometer tube 

 above the mercury. If, notwithstanding, the oxide shall accu- 

 mulate to an inconvenient extent, the observer in charge of the 

 instrument will remove the thermometer from its place, and will 

 put the bulb in warm water until the oxide is floated off. He 

 will then supply the loss with pure mercury, determining the 

 proper quantity by immersing the bulb in broken ice, when the 

 mercury column should stand at the mark for 32°. 



The whole apparatus, except the thermometer itself, can be 

 inclosed, and so protected from the weather and dust, while the 

 thermometer is exposed to the air below. 



The system is equally applicable to a barometric record, in 

 which case, on account of the small range of motion, the 

 needle-bar is connected to a lever, thus increasing the range of 

 the record. 



SCIENCE IN BOHEMIA » 

 '"THE Bohemian Society of Science continues its useful career, 

 which has already lasted for eighty-four years, and its 

 latest publications (the Memoirs, the Proceedings, and the annual 

 1 "Abhandluogen der Mathematish-Wissenschafllichen Classe der K. 

 Bi'ilimischen Gesellschaft der Wissenschaften, vom Jahre 1879-1880, vi 

 Folge, Band x. (Prag. 1881). " Siuungsberichte" of the same Society, for 

 1S79 and for 1880. " Jahresberichte " if the same, for 1879 and 1880. 



Reports) contain many valuable papers, devoted partly to science 

 in general, but mostly to the exploration of Bohemia itself in 

 its various aspects. The last volume of its Memoirs (" Abhand- 

 lungen" for 1879-1880, series vi. vol. x.) contains a series of 

 very interesting papers, each of them being the result of careful 

 and extensive research. Prof. Franz Farsky gives the results of 

 varied experiments which were undertaken at the experimental 

 agricultural station at Tabor, on the growth of food-plants in 

 water containing solutions of those salts which constitute the 

 ash of the plant. The influence of alkaline and acid solutions, 

 and especially that of chlorine, which proved to be a most im- 

 portant element of vegetation, were submitted to varied experi- 

 ments, all the results of which are published in full. The 

 general reader will notice with interest the beautiful results 

 obtained by the culture of oats and barley in glasses of water, 

 which contained the necessary salts, the plant being simply 

 planted in a bit of cotton. Dr. F. J. Studnicka publishes in the 

 same volume the complete tables of observations on the amount 

 of rain in Bohemia during the years 1S79 and 1S80, at no less 

 than 312 stations in 1879 and at 289 stations in 1880. If we 

 remember that besides these stations there are very many others 

 established by the Bohemian Foresters' Society, and that the 

 whole number of stations where the amount of rain is accurately 

 measured day by day, amounts to 800, we can see that Bohemia 

 has probably the widest network of ombrological observations 

 in Europe, We notice that the most rainy places in Bohemia 

 are Maader, Rehberg, and Neuwelt (1744, 1572, and 1505 milli- 

 metres per year respectively), all these situated at great heights 

 (9S5, 848, and 683 metres), whilst the less rainy places are 

 Rapic, Slaten, and Kladno (431, 43S, and 456 millimetres), 

 situated respectively at altitudes of 322, 246, and 380 metres. 



Dr. F. Ullik contributes a paper on the matter suspended and 

 dissolved in the water of the Elbe, at Tetschen. Samples of 

 water were taken three times every day, and the samples of each 

 day were analysed separately with regard to the matter sus- 

 pended, as well as to the quantity of chlorine, ammonia, nitric 

 acid, and organic substances. Besides, 22 complete analyses of 

 different types of water, and 12 of ooze, weie made. The 

 ssing through the Elbe at Tetschen proved to be 

 9,90;, 5 10,660 cubic metres during the year October 15, 1S76, to 

 October 15, 1877), which contained 776,309,959 kilograms of 

 suspended or dissolved matter. During the year 1877, the 

 amount of water run was 9,456,939,810 cubic metres, which 

 contained 36, 557 metrical tons of K-O, 69,631 tons of Na'O, 

 266,081 tons of CaO, 48,915 tons of MgO, 120,553 tons °* 

 SO 3 , 83,336 tons of chlorine, 778 tons of ammonia, and 

 11,196 of nitric acid. As to the sources of these im- 

 111en.se quantities of mineral substances, Dr. Ullik points 

 out that the amount which is supplied by waste water of 

 manufactures and sewage is usually over-rated. Thus, if 

 the well known sulphuric acid manufacture at Aussig would 

 pour all the acid it produces into the Elbe, it would give 

 only 5000 tons of SO 3 per year, that is, only the 24th part of 

 sulphuric acid anhydride contained in the waters of the river. 

 The amount of mineral substance poured into the river by all 

 the breweries of Bohemia would give only 401 tons per year, 

 that is, the 1562nd part of all the minerals contained in the 

 Elbe water. An 1, if all mineral substance contained in the 

 sewage from the 5,000,000 inhabitants of Bohemia would reach 

 the Elbe, it would yield only 33,250 tons, that is, i-20th of what 

 is really contained in the water of the river. Therefore, it is 

 obvious that the chief source of these substances in the river- 

 water must be sought for in the supply brought in by springs. — 

 Dr. Siegmund Glinther contributes to the same volume an inter- 

 esting notice on the " Algorithmic Linealis," by Heinrich 

 Strbmer, which appeared in 1512, being one of the products 

 of the revival of taste for mathematics which characterises, in 

 Germany, the beginning of the sixteenth century. The same 

 volume contains an elaborate paper on the Christian Calendar 

 and on the methods of improving it, by Dr. W. Matzka ; and a 

 notice on the electrical clock of Rebicek, by Dr. A. Walten- 

 hofen. It is worthy of notice that all papers that appear in the 

 AbhandUiHgcn ate written in German, and are so'd by the 

 Society as separate pamphlets. 



The Sitzungsberichte, or Proceedings, contain such a mass of 

 valuable papers that w e can notice only the more important of 

 them. They are especially rich in mathematics, and we find (in 

 the volume for the year 1879) papers by Dr. S. Giinther, on the 

 application of orthogonal co-ordinates to one problem of the 

 potential theory ; on the normals to parabola;, by Dr. K. 



