June 22, 1883.] 



SCIENCE. 



579 



beneficial influence on the advance of tliis in- 

 dustry in California, and vany fulfil the hopes of 

 their authors bj- leading to the establishment 

 of definite and reliable brands of California 

 ■wines. 



The -whole report, while dealing largelj" with 



questions of local interest, affords at the same 

 time an admirable illustration of the advantage 

 accruing to agriculture from the application 

 of high scientific attainments to the investiga- 

 tion of its problems. 



WEEKLY SUMMARY OF TEE PROaRESS OF SQIENGE. 



ASTRONOMY. 

 Semi-diameter of the moon. — Professor H. M. 

 Paul, formerly assistant at the U. S. naval observa- 

 tory, gives the resiiUs of two occultations of the 

 Pleiades group by the moon, observed by himself to 

 determine the occultation xemi-dlameter of the moon, 

 and also the corrections to the right ascension, 

 declination, and parallax of the moon, these being 

 necessarily involved with the semi-diameter. Tlie 

 occultations occurred on July 6, 1877, and Sept. 6, 

 1879, and were observed with the 9.6-incli equatorial 

 at the Washington observatory. The relative posi- 

 tions adopted for the stars were those of Wolf with 

 proper motions from comparison with Bessel, and the 

 general proper motion of the group as given by New- 

 comb. The observations of 1877 were poorly placed 

 for a determination of the correction to the semi-di- 

 ameter, but those of 187!) give a much more reliable 

 result. From the latter (fourteen in all), the result- 

 ing correction to Hansen's mean semi-diameter (15' 

 33 . 47) is — 1". 69 ± U". 12; and the resulting value 

 is, therefore, semi-diameter = 15' 1". 78 ± 0". 12. He 

 gives also the results of Airy's determination from 

 two hundred and ninty-six scattered observations, 

 from 18.30 to 1860. From the immersions and emer- 

 sions at the dark limb, the resulting values are larger 

 by 0".9 and 0".5 than those given by Paul, and, from 

 immersions and emersions at the bright limb, Airy's 

 results are larger by 2". 3 and 4".^; while the prob- 

 able error of a single observation and of the final 

 result is in all cases greatly in excess of those ob- 

 tained by Paul. Mr. Paul concludes that the best 

 way to observe tlie actual occultation at the bright 

 limb is to itse as high a magnifying power as possible, 

 so as to obtain a decided difference of color between 

 the star and the uionn's limb. Neither set of occul- 

 tations observed by Paul gives any evidence of devia- 

 tion of the moon's limb from a perfect circle. — ( Rep. 

 Wash, obs., 1S79, appendix ii.) m. mcx. [1103 



ENGINEERING. 



S^welled rifle-barrels. — A board of ofiiceis, witli 

 Capt. Greer as president, has tested a lot of rifles at 

 the Springfield armory to determine the cause of the 

 'bulging of the barrel, wliich occasionally occurs in 

 practice. They find it due to the fact that tlie muz- 

 zle has been stopped by sand, caused by resting the 

 muzzle in wet sand, or in dry sand after the gun has 

 become foul from firing. This arrests the passage of 

 the ball, so that the pressure is increased at the point 

 of swelling. It is curious that sand produced this 

 result where wooden plugs, driven in tightly and 

 swelled by steam, failed to do so. — [Ord. notes, 

 f/.S./l., no. 2-38, Feb. 1.) c. E. .M. [1104.- 



Strength of explosives. — Gen. Abbot lias ex- 

 tended his investigations to tonite, California gun-cot- 

 ton, and rackarock. The first consists of 52.5 parts of 

 gun-cotton and 47.5 parls of barium nitrate. The 

 second is gun-cotton pulverized, and containing 24 



per cent of moisture. The dry gun-cotton analyzed 

 89.0 per cent insoluble trinitrocellulose and 10.4 per 

 cent soluble gun-cotton. This is 7 per cent above 

 the standard required by the British government. 

 The rackarock is composed of piotassium chlorate and 

 nitrobenzol. The substances are kept separate until 

 needed for use, when the chlorate is dipped in the 

 liquid until it has absorbed enough of it. Gen. Abbot 

 found the relative efficiency in a liorizontal plane for 

 tonite, as compared with dynamite No. 1, to be 0.81 for 

 the dry compressed state, and 0.85 for the damp un- 

 compressed state, or 0.83 as the average value. It 

 thus stands just below gun-cotton (0.87). Rackarock 

 gives 0.86. The California gun-cotton was found 

 equal to the best English. In a note, he calls atten- 

 tion to the spontaneous decomposition of explo.^-ive 

 gelatine into cellulose and free nitro-glycerine, with 

 the evolution of nitrons fumes, while in store during 

 the winter ami spring. — (Prof, papers corps enq., 

 i7.S.^., no. 23, add. i.) c. B. M. [1105 



Composition of steel. — Professor Abel has con- 

 tinued his researches on steel; and his experiments 

 with cold-rolled steel of a particular composition con- 

 firm the view that the carbon exists in it in the form 

 of a carbide which has the formula FcjC, or some 

 multiple of that formula. Whether this carbide va- 

 ries in composition in different descriptions of steel 

 which are in the same condition of prepai'ation re- 

 mains to be demonstrated ; but the preliminary experi- 

 ments with small specimens of cold-rolled, annealed, 

 orliardened steel, appeared to warrant the belief that 

 the condition of the carbide in the metal is affected 

 to such an extent, by the process of hardening, as 

 moi'e or less completely to counteract its power to 

 resist the decomposing effect of such an oxidizing 

 agent as chromic-acid solution. — [Proc. hist. mecTi. 

 e/i(/., Jan., 1883.) c. E. M. [1106 



CHEMISTRY. 



{Analytical.) 



Preparation of hydric sulphide from coal-gas 



— Wheu coal-gas is passed through boiling sulphur, 

 I. Taylor finds that nearly all the hydrogen (forty to 

 fifty per cent) is converted into hydric sulphide. He 

 states that this is a convenient method for the prepa- 

 ration of hydric sulphide for laboratory use. — ( Cliem. 

 neujs, xlvii. 145.) c. F. M. [1107 



Hydric peroxide as a reagent in chemical 

 analysis. — A. Classen and O. Bauer find that the 

 great oxidizing power of hydric peroxide may be 

 made available in many quantitative determinations 

 which depend upon oxidation. Roth & Co. of Berlin 

 manufacture a three or four per cent solution, acidi- 

 fied with hydrochloric or sulphuric acid, as may be 

 desired. In an amuioniacal solution, hydric peroxide 

 oxidizes hydric sulphide completely. This reaction 

 affords a convenient and extremely accurate means 

 for the determination of hydrochloric, hydrobromic, 

 or hydriodic acid, in presence of hydric sulphide. 



