SCIENCE. 



357 



carried at the rate of half an inch per hour from right to 

 left by a clock. 



There is a third steel spring of the same length and 

 strength as those on the reservoir, stretched by a weight 

 to a distance equivalent to 30 inches on the barometer 

 scale. The object of this spring is to give the correction 

 of temperature for those sustaining the reservoir. The 

 register paper should always be set to the same line on 

 which the pencil of this spring marks. 



The movements of the mercury on the register can be 

 magnified to any required extent by increasing the length 

 of the spiral springs. In this instrument it is multiplying 

 twice. 



DESCRIPTION OF INSTRUMENT. 



The tube marked a b is of glass ; the upper part is of a 

 larger diameter than the stem, a being }( of an inch in- 

 ternal diameter and 10 inches long, while the stem,<5, is 

 Y% of an inch bore and 26 inches long. The total length 

 of the tube is therefore 36 inches. The reservoir, c, is 

 suspended from a brass frame, d, fastened to the back of 

 the case. This frame also holds the upper ends of the 

 steel springs, e, e, c. The glass reservoir, c, is of the same 

 diameter and length as the upper part of the tube, a ; on 

 its open end is turned a flange to hold it in a brass frame, 

 /, to which are fastened the lower ends of the steel 

 springs, e e ; it also carries an ink pencil,^, that touches 

 the ruled paper on the board h h, which is drawn aside 

 by the clock, i. The spring, e, is for the correction of 

 temperature on the other springs. Heat has a slight 

 effect on them, causing them to lengthen about of an 

 inch from 90 degrees Fahr.; to allow for this, the third 

 spring, c, is weighted with a lead weight and pencil, it 

 marks its fluctuations on the upper line of the register 

 sheet. In this manner this instrument gives the correc- 

 tion for temperature (or reduction to 32 ) from the fact 

 that it weighs the mercury instead of measuring its length, 

 which is affected by heat. 



Ink pencils of the barometer and other instruments are 

 made by drawing narrow glass tubing to a fine point, 

 which lightly touches the paper register, leaving a mark 

 of red ink that has been diluted with about one quarter 

 of its volume of glycerine. The glycerine prevents the 

 ink from drying too rapidly. The advantage of this form 

 of pencil over lead ones is that it requires little or no 

 pressure to produce a mark. 



To receive the atmospheric fluctuations a suitable 

 ruled paper is fastened by means ot small brass clamps, 

 k k, to the board, h h, which is hung by rollers to the 

 thick steel rod fastened to the sides ot the case, on which 

 the paper : s carried from right to left by the clock, i, at 

 the rate of % an inch per hour, by means of the pulley 

 on the hour arbor of the clock. The wire that connects 

 the register board to the clock is soft steel, number 28 

 wire gauge ; having only one turn round the pulley 

 it readily slips so that the board can be pushed sideways 

 for the adjustment of time, or for the renewal of the sheet 

 of paper." 



ON AN OCCURRENCE OF GOLD IN MAINE* 



By M. E. Wadsworth. 



The gold under consideration here is found on Sew- 

 ard's Island, a small island in the town of Sullivan, 

 Hancock County. The gold is found in quartz veins 

 cutting an eruptive mass of diabase. This diabase forms 

 a dike of about forty feet in thickness, lying approxi- 

 mately paralhl to the bedding of an indurated fine- 

 grained argillaceous mica schist ; all dipping nearly S. 

 30 W., 24' to 42 . The dip averages about 35°, and the 

 strike is far from being uniform. Crossing the diabase 

 at various angles, but generally from north to south, are 

 segregated quartz veins. In some places the rock is a 



* From the Bulletin 0/ the Museum 0/ Comparative Zoology.— har- 

 vard College, 



confused reticulated mass of these veins, with patches 

 of diabase lying between them. The veins vary in 

 width from a mere seam to even a foot in breadth. 

 Starting where only one or a few of them are visible, 

 they gradually increase in number, until they be- 

 come quite numerous, while they will doubtless be 

 found to fade away as they began. The diabase 

 and schists are cut by several dikes of diabase 

 running approximately at right angles to the strike of the 

 schist, or parallel to the veins. The vein stone is quartz, 

 together with some calcite, tremolite and chlorite, and 

 carries tetradymite and gold. 



So far as examination has been made, the veins in 

 the diabase carry gold, and the decomposed diabase im- 

 mediately adjacent to the quartz veins also contains that 

 metal to a greater or less extent. The gold occurs prin- 

 cipally in small grains in the vein in conection with the 

 tetradymite, bits of decomposed diabase, and in the 

 cavernous portions, but not in the compact quartz of the 

 vein itself. The tetradymite is in irregular grains and 

 masses, showing a brilliant metallic lustre, and a well- 

 marked basal cleavage. The locality is worked for it 

 gold, and was visited by the writer in December last 



Cambridge, Mass. 



ELEMENTS AND EPHEMERIS OF COMET 

 (c), 1881.— SCH^BERLE. 



The elements and ephemeris of the comet, given be- 

 low, are those computed at the observatory of Lord 

 Crawford, at Dun Echt, Scotland, and cabled to the 

 Science Observer by means of the code adapted by S. C. 

 Chandler, Jr., and John Ritchie, Jr. 



ELEMENTS. 



Perihelion Passage, 1881, Aug. 2i d .50. Greenwich 

 Mean Time. 



Long. Perihelion = 218 45 "I 



Dist. Perihelion from Node =121 o r oc 



Long. Node = 9 7 3 g j" Eq. 1881. o. 



Inclination = 140 37 J 



log. Perihelion Distance, 9.8069. 



EPHEMERIS. 



Greenwich midnight R.A.— s — Decl.— > 



1881. h. m. s. 



Aug. 3 6 43 4 + 47 46 



7 7 11 24 50 11 



11 7 54 56 52 20 



15 8 59 24 52 57 



Computed by Drs. Copeland and Lohse, at Dun Echt 

 Observatory, from observations at Vienna and Dun Echt. 



The following elements have kindly been furnished by 

 Prof. Ormond Stone, of Cincinnati : — 



T = 



August 19.202. 



a = 



1 a 

 122 30 21 



Q — 



98 42 41 



* = 



141 35 2 



log. q = 



9.79590. 



Science Observer Special Circular No. 16 



The following simple electrical experiment is described 

 in L Elcclricien. A small box of pasteboard is closed with 

 a lid of fine glass, on the upper surface of which collodion 

 is applied several times (but not so much as to render the 

 lid opaque). In the box are placed insect forms, made ot 

 sponge or cotton. On rubbing the collodion surface with 

 dry ringers, in dry weather, the insects move about in a cu- 

 1 rious manner. 



