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NATURE 



[July 25, 1878 



the practical bearings of the science, viz., the relations 

 of the barometric depressions and storms of the Pacific 

 States to the storms east of the Rocky Mountains. As 

 regards the twenty-seven storms whose courses he has 

 traced, it is probable that the great majority, if not the 

 whole of them, were first formed over the Pacific Ocean, 

 In each of the twenty-seven cases (with perhaps one 

 single exception) the storm crossed the Rocky Moun- 

 tains, and was thence tracked across the United States 

 to the shores of the Atlantic, subject, however, in some 

 cases to modification in its progress. It is scarcely pos- 

 sible to overrate the importance of these results in the 

 practice of weather telegraphy and on questions affect- 

 ing the general movements of the atmosphere. For we 

 see here that an unbroken mountain-range of at least 

 6,ocx3 feet in height does not stop the eastward progress 

 of these barometric depressions and storms ; neither do 

 mountain-ranges of more than 10,000 feet in height, 

 broken as in North America, present an insuperable 

 obstacle to the onward course of these phenomena. The 

 mountain-ranges between the Pacific and the Mississippi 

 present obstructions to the formation of a system of 

 winds of any great geographical extent ; and hence, pro- 

 bably, barometric depressions are not so great over this 

 uneven and broken region as over the vast plains of the 

 Mississippi and eastern States, where there are no 

 mountain barriers to interfere with the formation of a 

 system of circulatory winds over areas 2,000 miles in 

 diameter. 



CHEMICAL NOTES 



Influence of Temperature on the Rotatory 

 Power of Quartz. — Following up the researches of 

 Lang and Fizeau, Sohnckd has found {Ann. d. Phys. 

 Chem., N.S. III. p. 516) that the increase in rotary 

 power in quartz, with increase of temperature, is not 

 directly proportional to the temperature, but is less at 

 lower than at higher temperatures. For the crystal he 

 experimented on he determined the following formula : — 

 tp — (p° {\ + o "0000999 ^ -f- o'oooooo3i8/^), 



where (^° = the rotatory power of the same crystal at 0° ; 

 and he further found that the relative increase of power 

 in the plane of polarisation was the same for all colours 

 up to 170°. To see whether the octahedral system pre- 

 sented the same phenomena he also examined common 

 salt, and obtained similar but more strongly-marked 

 results. 



Change of Indices of Refraction in Mixtures 

 of Isomorphous Salts. — M. Dufet, in the Comptes 

 RendiiSi Ixxxvi. 881, gives a most interesting account of 

 some experiments he has carried out on the above subject, 

 partly in continuation of such work as that of Senarmont, 

 Topsoe, and Christiansen {Ann. Chem. Pharm., 1874). 

 Instead of examining simple isomorphous salts the author 

 has taken mixtures containing varying quantities of mag- 

 nesium and nickel sulphates, but of known composition. 

 Working with such bodies he has determined that " the 

 differences between the indices of a mixture of two 

 isomorphous salts and those of the component salts are 

 inversely proportional to the number of equivalents of 

 the two salts entering into the mixture." In his calcula- 

 tion, M. Dufet has taken as an equivalent the number 1 1 1 

 or one equivalent of SO4.7HO. He considers the law of 

 variation of the index as a consequence of Gladstone's 



of a mixture of two 



D 



law : the refractive energy 



bodies with no chemical action on one another, being the 

 sum of the refractive energy of the component sub- 

 stances. According to M. Dufet, isomorphous salts 

 crystallising together, form mixtures presenting analogies 

 to a certain extent comparable with liquid mixtures, 

 where the physical properties^are the mean of those of 



the components ; this, however, is only true up to a 

 certain point. 



Allotropic Modification of Copper.— By the 

 electrolysis of a solution of about 10 per cent, of copper 

 acetate Schiitzenberger has obtained an allotropic variety 

 of copper somewhat remarkable in its physical and che- 

 mical properties. During the electrolysis the surface of 

 the negative platinum electrode which faces the positive 

 copper electrode becomes covered with a layer of the 

 allotropic modification of the metal, whilst the other side 

 of the electrode is covered with a deposit of ordinary 

 copper. The allotropic modification forms metallic 

 glittering scales with roughened surfaces on the side next 

 the solution ; should the electrolysis be carried on long 

 enough, beautiful tree-like forms are deposited on the 

 edge of the negative electrode, which gradually ramify 

 over to the positive electrode. The allotropic copper is 

 less red than the ordinary variety, possesses surfaces 

 without malleability, and can be reduced to an extremely 

 fine powder. Its density, 8 to 8*2, is higher than that of 

 the ordinary variety, which is about &g. It oxidises 

 rapidly in the air, becoming at once iridescent, and 

 finally of an indigo blue colour ; when exposed to the air as 

 a powder it becomes black, changing finally into the 

 oxide. According to the author it becomes reconverted 

 into the ordinary form of copper by heat, or exposure to 

 certain chemical agents. 



Saccharose.— M. J. Motten has recently brought for- 

 ward a paper, entitled a " Contribution to the History of 

 Sugar (Saccharose)," in which the author discusses the 

 action of light and of a temperature of 100° Cels. on solid 

 and dissolved sugar, proving that the light alone does not 

 invert dissolved sugar, and also that a temperature of 

 100° does not alter dry sugar. On the other hand solid 

 sugar imperfectly dried, and dissolved sugar are altered 

 under the influence of that temperature ; oxygen is then 

 absorbed, and carbonic acid evolved, but more slowly 

 than it was often supposed. 



Heat Evolved in the Formation of Isomeric 

 Bodies. — M. Berthelot has given several communica- 

 tions to the Chemical Society of Paris, relating to the 

 above subject. He finds that in general nitro compounds 

 and isomeric nitric ethers appear to be formed with the 

 disengagement of very unequal quantities of heat ; the 

 transformation of ethers into nitro compounds disengage 

 approximately thirty heat units, at the same time under- 

 going increase of density and rise in the boiling point. In 

 the case of metameric acids, as butyric, isobutyric, vale- 

 rianic, &c., combining with the [same base, his numbers 

 show that the heat disengaged is precisely the same in the 

 various cases which he describes. Approximately equal 

 numbers are also obtained in the case of the chloro and 

 bromo derivatives of these acids. There is very little differ- 

 ence also in the heat disengaged in the transformation of 

 isomeric alcohols into isomeric aldehydes. The general 

 results of his experiments, covering about thirty com- 

 pounds, including alcohols, aldehydes, fatty acids, and 

 their salts, chloro and bromo acids, &c., point to the 

 conclusion that isomeric bodies having the same chemical 

 function are formed with nearly identical disengagements 

 of heat, their reciprocal metamorphosis disengaging very 

 little heat. Finally, the same approximations exist in the 

 formation of their isomeric derivatives. 



Chemical Changes Taking Place during the 

 Ripening of Grapes. — From experiments lately made 

 on the transformations of the grape, and the exchanges 

 between it and the surrounding atmosphere, MM. Saint 

 Pierre and Magnien conclude that grapes at the time of 

 their maturation liberate carbonic acid both in darkness 

 and in light, the quantity produced being always superior 

 to the quantity of oxygen consumed, if the experiment be 

 long enough. This liberation occurs as well in an inert 



