176 



SCIENCE. 



[Vol. II., No. 27. 



The same law holds for zinc and zinc sulphate, cad- 

 mium with its acetate, and lead with its acetate; but 

 for silver, with its sulphate, nitrate, and acetate, the 

 law is reversed. In a Daniell cell, a fortiori, less heat 

 is used for formation of current than is set free in 

 the chemical action of the cell. — {Ann. phys. chem., 

 xix. 287.) J. T. • [177 



CHEMISTRY. 

 (General, p/iytiical, and inorganic) 

 Speed of dissociation of brass. — Mr. E. 

 Twitchell (under Prof, Robert B. Warder's direc- 

 tion) made the following determinations, which 

 were suggested by Bobierre's method for the separa- 

 tion of copper and zinc in alloys. A piece of brass 

 wire (no. 17) 1-50 mm. long and 1.43 mm. in diameter 

 was heated to redness in a stream of hydrogen in a 

 porcelain tube. The loss in weight, from hour to 

 hour, is given in the following table: — 



The figure* given under A are proporlional to the 

 'coefficient of speed,' as calculated from each obser- 

 vation, on the hypothesis that the zinc e.Kpelled at 

 each moment is proportional to the whole quantity 

 of zinc present. The steady decrease in the last 

 column shows that this hypothesis does not obtain 

 under the conditions of the experiment, hut that an 

 appreciable interval of time is required for the trans- 

 fer of zinc from the central portion to the surface of 

 the wire. Further experiments upon this diffusion 

 of zinc are in progress. — (Sect. chem. phys. Ohio 

 mech. inst.; meeting May 31.) [178 



AGKICULTUEB. 

 Influence of temperature and rainfall on the 

 ■wheat-crop. — A comparison of the average tem- 

 perature and the rainfall in England during the 

 months of July and August for the last thirty-six 

 years, with the corresponding wheat-crop, justifies the 

 following conclusions: provided the stand of the crop 

 at the beginning of July is promising, a tempera- 

 ture above the average for the succeeding two months 

 insures more than an average crop as regards quan- 

 tity, unless extraordinary circumstances, such as vio- 

 lent storms, intervene. Rainy weather may reduce 

 the quality of the crop. On the other hand, however 

 promising the crop may be at the end of June, a 

 temperature below the average in July and August 

 involves a small crop. If the weather is clear, the 

 quality may be gooil, while, if cold and rain are 

 united, the poorest crops are the result ; such as those 

 of 1879, when the temperature was 2.8° F. below the 



average, and the rainfall four inches above the aver- 

 age, or that of IttlG (the poorest crop on record), when 

 the temperatuie was 4.8° F. below the average. — 

 {Bied. ceiitr.-blalt., x\i. 291.) n. p. A. 1179 



Effect of phosphatic manures in drought — 

 In the course of some field-experiments made during 

 the very dry season of 1881, Emmerling observed that 

 in one case manuring with ammonia alone produced 

 a greater. gain than manuring with ammonia and 

 superphosphate. The result may have been acci- 

 dental, as no duplicate trials seem to have been 

 made ; but Emmerling thinks that tlie manuring with 

 phosphoric acid hastened the ripening of the plants, 

 while the ammonia had the opposite effect of post- 

 poning the ripening, and keeping tlie plants green 

 longer. (This effect of phosphoric acid has been ob- 

 served in water-culture experiments, and silica also 

 seems to exert a similar action.) — {Bied. centr.-blatt., 

 xii. 297.) H. p. A. [180 



Damage to grain by ■wetting. — Milrcker has 

 examined a sample of barley which had been exposed 

 to rain for fourteen days after it was cut. A consid- 

 erable proportion of the starch had been converted 

 into sugar. A loss of about six per cent of starch 

 took place. The albuminoids were also altered, both 

 the insoluble and soluble proteine having been par- 

 tially converted into amides. The proportion of seed 

 capable of germination was reduced from ninety-eight 

 per cent to forty-five per cent. Kobus obtained sim- 

 ilar results in an examination of damaged wheat. — 

 (Bied. centr.-blatt., xii. 826.) h. p. a. [181 



MINERALOGY. 



Enclosures in muscovite. — The occurrence of 

 hiotite and muscovite in one crystal is well known, 

 and has been investigated by H. Carvill Lewis. He 

 prepared cleavage-sections from one specimen, and 

 arranged them in the order in which they occurred. 

 The biotite contrasts strongly with the light-colored 

 muscovite, and has often well-defined edges. The 

 two micas are arranged symmetrically in relation to 

 their prismatic planes, as may be shown by the crys- 

 tal edges when they are well developed, or by the 

 strike-figures which are parallel in the two micas in 

 the same folia, making it probable tliat they have 

 crystallized together out of the same solution. In 

 examining a series of sections from one specimen, it 

 is found that the proportion of the two micas varies 

 in different parts of the crystal; the biotite, the more 

 unstable of the two species, gradually giving way, and 

 being changed into the more hardy muscovite. 



Of a different nature are the superficial markings 

 of magnetite, which occur from various localities. 

 These markings form a series of branching lines, 

 which run in three directions across the plates of the 

 mica, crossing each other at angles of 6l)°, and have 

 been regarded as repeated twinning around a dodeca- 

 hedral axis. These lines, however, as shown by the 

 author, bear a fixed relation to the axes of the mica, 

 and are not due to any inherent property of the mag- 

 netite. If a crystal showing these markings be dis- 

 sected, the lines of marking will all be found to lie in 

 parallel direction ; nor is there any direct connection 



