24 



SCIENCE. 



sity greater than that of granite, as well as a strong co- 

 hesive force between its parts, in order to withstand' the 

 tendency to disintegration during its perihelion passage. 

 Had the nuclus been either liquid or gaseous, or even a 

 cluster of solid meteorites, the difference between the I 

 sun's attraction on the central and the superficial parts 

 would have pulled the comet asunder, spreading out the 

 fragments into somewhat different orbits, like the mete- 

 oric streams of August and November. — The Analyst. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. No notice is taken of anonymous communi- 

 cations.'] 



To the Editor of " Science :" 



I have much pleasure in enclosing you a copy of the 

 particulars respecting the formation of our " Field Club," 

 which I believe to be the third in England of similar pre- 

 tentions, its original founders being Mr. Thomas Kiddie 

 and myself, both being science students, and by profes- 

 sion analysts in manufactories on Coaly Tyne. We were 

 at first inclined to restrict the Club to those of our own 

 class, namely, Students in Chemistry, but knowing the in- 

 timate connection between all the other branches of 

 Science and that of Chemistry, we determined to throw it 

 open to all science students, and we are now pleased to 

 find that our efforts have had such a successful issue so 

 far, and met with such general approval throughout the 

 whole district, as we have at present, after two months 

 establishment, about 100 members, some living as far as 

 fourteen miles from our centre ; also having the counte- 

 nance of fourteen gentlemen interested in scientific edu- 

 cation as honorary members. The officers consist of 

 students or teachers (under the Science and Ait Depart- 

 ment, London). Should you consider our club worthy a 

 comment in your excellent journal, which latter must act 

 as a valuable adjunct to the aims of scientific education, 

 I shall be exceedingly obliged if you will forward me a 

 copy to read at one ot our excursions. 



M. Theodore Dixon, Hon. Sec. 



5 Brandling Park. Newcastle-on-Tyne, Eng. 



[We print the above letter in the hope that it may sug- 

 gest the formation of Field Clubs in the United States. The 

 value of such organizations cannot be overrated, and we 

 shall be glad to hear that some of our subscribers have 

 taken the initiative in such an agreeable enterprise. 'We 

 shall send information to those who desire it. — Ed.] 



CHEMICAL NOTES. 



The Marquis Tommassi has succeeded in sending a 

 message across the Atlantic with two Minotto elements. 



An Application of Accidental Images.— J. Plateau, I 

 from some experiments performed by his son, concludes j 

 that the apparent distance of the full moon is only 50 metres 1 

 from the observer. 



Propagation of Light. — M. Gouy has shown that there 

 is not, for a given homogeneous source, a determined 

 speed of light independent of the manner in which the am- I 

 plitude is caused to vary. 



Phylloxera in France. — It appears that more than a 

 third part of the vines in France have been already de- 

 stroyed by the phylloxera. The departments of Haute < 

 Savoie and Jura are now attacked. 



Spontaneous Oxidation of Mercury and of Metals. 

 — Mercury, as well as iron, zinc, cadmium, lead, copper, 

 and tin, undergoes on exposure to the air a superficial oxi- 

 dation, very slight, an! restricted by the difficulty of renew- 

 ing the sutfaccs and by the want of contact which results 



from the layer of oxide formed at the outset. For the oxi- 

 dation to continue this layer must be constantly removed, 

 as in the case with rust of iron formed in moist air, or for 

 each hydrocarbonate produced in distilled water. — M. 



Berthelot. 



Wines Mixed with Grape Sugar. — The non-ferment- 

 able part of the grape sugar which is introduced into wines, 

 if administered to dogs by way of subcutaneous injection 

 produced vomiting and other morbid symptoms. A. 

 Schmitz claims that these residues contain a poison similar 

 to that present in potato-oil. 



Action of Phosphorous upon Hydriodic and Hydro- 

 bromic Acids. — With hydriodic acid and white phosphor- 

 ous the latter melts and becomes covered with a reddish 

 layer of biniodide, while phosphonium iodide sublimes. 

 With red phosphorous even at ioo°, there is produced 

 merely a small quantity of phosphonium iodide. Upon 

 dissolved hydrobromide acid, phosphorus does not react 

 in the cold. At from 100' to I20 = , phosphonium bromide 

 sublimes, but no phosphorous bromide is produced. — 

 A. Damiseau. 



The Societe d'Encoukagement pour l'Industrie Na- 

 tionale has awarded the Le Blanc prize of 1000 francs 

 for the utilization of manufacturing refuse to M. Vincent, 

 for his process for obtaining methyl chloride from the 

 vinasses of the beet-root sugar manufacture. A sum of 

 1000 francs has also been awarded to M. J. A. Martin for 

 his mixtures for rendering textile articles, paper, &c, unin- 

 flammable. His ordinary mixture for light goods is : 

 Pure ammonium sulphate, 8 kilos ; ammonium carbonate, 

 2 kilos, (5); boric acid, 3; pure borax, 2; starch 2 (for 

 which may be substituted 0.400 kilo, dextrine, or the same 

 weight of gelatine), and water 100 kilos. A silver medal 

 has been awarded to M. Idrac for his process of drying 

 timber. 



A New Electric Property of Selenium, and the Ex- 

 istence of Tribe-Electric Currents Properly So- 

 called. — R. Blondlot has observed a new electric property 

 of selenium which may be shown by the following experi- 

 ment: To one of the poles of a capillary electrometer 

 there is attached, by means of a platinum wire, a fragment 

 of selenium which has been recently heated, and to the 

 other pole a platinum foil. If the selenium is brought in 

 contact with the platinum, holding it by means of an isolat- 

 ing handle, the electrometer remains at zero, as might be 

 expected from the symmetry of the circuit ; but if the selen- 

 ium is rubbed against the surface of the metal the elec- 

 trometer deviates strongly, the deviation obtained being 

 equal to that produced by a sulphate of copper element. 



Analysis of Superphosphates. — In acting upon a 

 superphosphate made of bone-black or from the phosphate 

 of Caceres with a solution of ammoniumcitrateofsp.gr. 

 1 '09, there is no occasion to take into account the time of 

 action or the fluctuations in the temperature of the labora- 

 tory. In the analyses of a bone-black superphosphate, an 

 excess of citrate must be avoided — 20 c.c. are sufficient 

 for 2 grms. of the sample. An excess of the reagent dis- 

 solves part of the phosphoric acid of such tricalcic phos- 

 phate as has escaped ttie action of sulphuric acid in the 

 manufacture of the superphosphate. The phosphate of Ca- 

 ceres is much less sensitive to the action of the citrate than 

 the phosphate of bone-black, and here from 20 to 100 c.c. 

 may be taken to 2 grms. of the sample. — L. Chevron. 



Determination of Chicory" in Ground Coffee. — M. 

 Prunier suggests the following method: Two grms. are 

 weighed out and separated from the finer powder by sifting 

 through fine silk. This powder which, as micioscopic ex- 

 amination proves, is composed entirely of pure coffee, is 

 set aside. That which remains on the sieve is macerated 

 with a few grms. of water in a test glass. After some 

 hours it is thrown upon a piece of cloth stretched out and 

 crushed with the fingers. The grains of coffee resist the 

 pressure, whilst those of chicory, reduced to a paste by 

 soaking in water, penetrate into the cloth and adhere to it. 

 On diving the cloth it is easy to detach the coffee, which, 

 after dessication at ioo° and addition of the fine powder 

 separated at first, gives the weight of pure coffee. The chi- 

 cory is calculated as loss. 



