80 Intelligence and Miscellaneous Articles. 



A NEW FOEM OF ABSORPTION-CELL. 

 BY ARTHUR E. BOSTWICK. 



The writer lias devised and used the cell described below for the 

 purpose of obtaining the absorption-spectra of liquids which have 

 but little selective absorption, and which would therefore have to 

 be used ordinarily in large quantities. 



The cell is a rectangular box about six inches long by three broad 

 and three in height. The bottom and the two ends are of pine 

 wood, covered with shellac, and the two sides are of ordinary 

 looking-glass, cemented to the wood, so that the box is water-tight. 

 The reflecting surface of the looking-glass is turned inward, and at 

 each of two diagonally opposite corners the amalgam is scraped 

 away so as to make a vertical slit about two millimetres in width. 

 One of these is placed close to the spectroscope-slit, and through 

 the other a parallel beam of light is admitted. It is evident that 

 the box may be so placed that the beam will be internally reflected 

 in it a number of times, depending upon the angle between the two, 

 and will finally pass through the second slit into the spectroscope. 

 The length of its path through the cell may therefore be varied 

 indefinitely by turning the latter, and is limited only by the decrease 

 in intensity caused by general absorption — not only in the liquid, 

 but also at each reflection. 



A solution of bichromate of potash, so weak that a test-tube 

 full of it was of a barely perceptible yellow colour and showed no 

 absorption at all when held before the spectroscope-slit, when placed 

 in this cell, absorbed the whole upper end of the spectrum, the F 

 line being scarcely visible. In this case sunlight was used, the 

 beam being reflected six times, and having a path whose length 

 inside the cell was about two feet. With mirrors of polished 

 metal the result might be even better, since the absorption in the 

 glass would be eliminated. In this case however the number of 

 liquids which could be used in the cell would be somewhat limited. 

 — Silliman's American Journal, December 1885. 



ON THE COOLING OF A WIRE WHEN STRETCHED. BY E. DORN. 



A steel wire about 0*7 millim. in diameter is clamped at the top, 

 while to the lower end is fixed a scale-pan in which weights can be 

 placed. Bound two adjacent places of the principal wire a thin 

 German silver and a steel wire are wound, the ends of which are 

 connected with the galvanometer in such a way that a thermo 

 element (steel-argentan) is formed. When weights are placed in 

 the pan the galvanometer shows a cooling, and a warming when 

 they are removed. With a Wiedemann's galvanometer, which was 

 almost dead-beat, arranged for objective representation, with lamp, 

 lens, and scale, I got a deflection of several centimetres. The 

 places of contact of the heterogeneous metals must be protected 

 from air-currents by means of felt. — Wiedemann's Annalen, 

 vol. xxvi. p. 334. 



