428 



SCIENCE. 



[Vol. I., No. 15. 



object-stand, and the weighted microscope-tube let 

 down upon it. There are three planes through the 

 principal axis, making angles of 120° with each other, 

 such that all pressures in these planes, or parallel to 

 them, produce minimum electricity at the points of 

 pressure. Pressure exerted perpendicular to these 

 minimum planes produces maximum electricity. 

 Each of the six fields into which the minimum 

 planes divide the sphere possesses the property that 

 all points of pressure within it are electrified to the 

 same sign: these signs are opposite in adjacent lields. 

 Pressure in the direction of the principal axis gives 

 each of the six fields its peculiar sign: pressure in 

 any other direction divides the sphere into two oppo- 

 sitely electrified halves, the plane of division passing 

 through the principal axis. No direction of pressure 

 produces electricity at the ends of the principal axis. 

 If the direction of pressure is a maximum axis, the 

 plane of division is the minimum plane perpendicular 

 to it (the signs of the halves correspond to the signs 

 of the fields in which the maximum axis lies); but, if 

 the pressure is in this minimum plane, the electrifi- 

 cation is exactly reversed. The experiments seem to 

 show, that, if the direction of pressure rotates about 

 the principal axis with an angular velocity u, the 

 plane of division rotates in the opposite direction with 

 a velocity 2 ok The author then shows that the 

 optical properties of quartz in an electric field can be 

 accounted for by the expansions and contractions 

 which quartz undergoes under electrical strain, ac- 

 cording to the principle of reversibility of piezoelec- 

 tric effects pointed out by Lippmann. This result 

 has also been reached independently by Kundt in 

 Ann. phys. chem., no. 3. — [Ann.phys. cjiem., no. 4.) 

 •J. T. [870 



Corrosion of steel. — Two chisels in the channel- 

 way of the U.S.S. Triana were badly corroded. Prof. 

 Munroe, U.S. N.A. finds this due to eleCtro-chemical 

 action between tempei'ed and untempered steel in 

 presence of salt water. The untempered steel suffered. 

 — {Proc. U. S. nav. inst., viii. no. 3.) c. B. M. [871 



ENGINEERING. 



Tensions in guns. — Considering the longitudinal 

 and hoop tensions in a thick hollow cylinder, Lieut. 

 Stone, U.S.N., finds that the longitudinal tension 

 is greatest on the outside, and the hoop tension is 

 greatest on the inside, where an assumed distance of 

 a point from the axis of the cylinder coincides with 

 the internal radius. He shows the presence of a 

 neutral surface, within which there is a longitudinal 

 compression, and without, a longitudinal tension. 

 The formula deduced, giving the value of the maxi- 

 mum hoop tension, differs considerably from that 

 heretofore used. The existence of a neutral surface 

 of longitudinal stress is of great interest in the con- 

 struction of built-ui3 guns. That a longitudinal con- 

 traction may accompany a circumferential expansion 

 is a familiar result of experiment. These formulas 

 may be used in calculating the tensions in built-up 

 wire guns. — {Proc. U. S. nav. inst., viii. no. 3.) 

 c. B. M. [872 



Lighting buoys and railroad-cars. — The U. S. 

 lighthouse board has placed a Pintsch lighted buoy at 

 the entrance of New- York harbor at the request of 

 the pilot commissioners. The Erie and the West 

 Shore railroads have adopted this method of lighting 

 cars in imitation of German railways. Gas made 

 from coal-oil is stored by compression in reservoirs, 

 and burned in peculiar burners, a regulator being 

 used to preserve the desired pressure. — (3farine reg.; 

 fi. iJ. f/az., April.) r. h. t. [873 



Heavy steel guns. — The chief of ordnance has 

 called for information from the steel-makers of the 

 United States, relative to the feasibility of making 

 steel for ordnance, giving analyses of desired qualities. 

 The act of 1883 provides for arming fortifications 

 with steel guns. — {Bull, iron steel assoc, April, 

 18S3. ) K. II. T. [874 



Standard gauge system. — G. M. Bond, M.E., 

 has described to the American society of mechanical 

 engineers the system of standardizing gauges devised 

 by Prof. Rogers of Harvard, and himself, for the 

 Pratt & Whitney company of Hartford, and the 

 comparator built for that company under their direc- 

 tion for establishing standard gauge measures. A 

 pair of standard inch-measures, woi'ked down inde- 

 pendently, were found to be exactly alike, the differ- 

 ence, if any exists, being less than -anTijoTi inch. 

 Bond reports ready for inspection by the committee 

 of the society, a set of end-measures varying by six- 

 teenths of an inch, and a complete plant of tools 

 and fixtures for producing standards, duplicating 

 originals by mac/iined work. — {Journ. Frankl. inst. , 

 May.) K. H. T. [875 



CHEMISTRY. 

 iAnali/tical.) 



Estimation of sulphur in organic bodies. — 

 P. Claesson has perfected a method for the deter- 

 mination of sulphur in organic substances, which 

 seems, from his results, to be capable of remedying 

 the various defects that detract to a greater or less 

 extent from the accuracy of the methods hitherto in 

 use. It consists in burning the substance in a cur- 

 rent of nitric dioxide and oxygen, and absorbing the 

 sulphuric acid in a receiver containing water. The 

 sulphuric acid may be determined by titration, or by 

 precipitation as baric sulphate. The substance is 

 placed in an ordinary combustion-tube, and behind it 

 a roll of platinized asbestos. In front of the sub- 

 stance are placed several platinized asbestos rolls, and 

 a small tube containing fuming nitric acid. The 

 combustion is conducted in the usual way, and finally 

 the sulphuric as well as the nitric acid is expelled 

 into the i-eceiver. The author adduces results to 

 show that a dilute solution of sulphuric acid may be 

 evaporated to dryness on the water-bath without ap- 

 preciable loss of the acid. — {Zeitschr. anal, chem., 

 xxii. 182.) c. p. M. [876 



Determination of lactic acid. — E. Palm states 

 that lactic acid is completely precipitated when it is 

 added in aqueous solution to an alcoholic ammonia- 

 cal solution of basic plumbic acetate. The plumbic 

 lactate is washed with alcohol, since it is somewhat 

 soluble iu water. — {Zeitschr. anal, chem., xxii. 223.) 

 c. F. M. ■ [877 



FloTW of liquids on the surface of a burette. — 

 In measuring liquids from a burette. Prof. E. B. 

 Warder finds that an error may be introduced by the 

 gradual rise of the meniscus, if the reading is taken 

 too soon after the flow of the liquid is stopped. 

 After a discharge of 60 cc. of a one-eighth normal 

 solution of sodic hydrate, the meniscus continued to 

 rise for ten minutes. — {Proc. Ohiomech. inst., ii.46.) 

 c. F. M. [878 



A new method for the determination of ar- 

 senic. — Mr. Richard Pearce, of the Boston and Colo- 

 rado smelting company, described a method for the 

 quantitative estimation of arsenic, as suggested by 

 himself, and developed by Albert H. Low, chemist of 

 the company. It consists in first fusing the mineral, 

 ore, or furnace-product supposed to contain arsenic, 

 with sodium carbonate and potassium nitrate, ex- 



