MICROSCOPICAL TECHNIQUE. 93 



a low power (Zeiss, A) to find two cells separated from each other 

 by a distance equal to, or less than, the radius of the smaller cell, 

 and from all other cells by a distance not less than about double 

 the diameter of the cells. No yolk substance should lie between 

 or beneath the cells. Such a pair of cells having been found, 

 higher objectives (Zeiss, C or D) may be turned upon them, and 

 the cell so adjusted under the ocular micrometer, that the line 

 connecting their centres will fall length-wise of the micrometer. 

 In this position, one can easily see whether the cells move towards, 

 or away from, each other. 



Microscopical Analysis of Steel.— At a recent conference held 

 under the auspices of the French Society for the Encouragement 

 of National Industry, M. Osmond described a method for the 

 microscopical analysis of steel. The method proposed comprises, 

 in addition to the preliminary process of preparing the polished 

 surface, three operations: (i) Polishing in bas-relief on parchment 

 with a very small quantity of English rouge mixed with water ; 

 (2) Etching and polishing on parchment with a mixture of calcium 

 sulphate, in precipitate, in a suitable vehicle ; and (3) Etching 

 with tincture of iodine and nitric acid. These three operations 

 enable one to recognise in the steel five constituents. These 

 five constituents are associated in combination to form the com- 

 plex edifice of the structure of steel. 



M. Osmond examined four types of steel, possessing a known 

 proportion of carbon, to discover the manner in which these 

 combinations varied. As a result of that investigation, M. Osmond 

 states that the thermic treatment of steel leaves in the structure of 

 the metal, when cooled, characteristic indications sufficiently 

 precise to form a useful guide in the manufacture of steel, and also 

 to enable consumers to determine the quality of the metal supplied 

 to them. — Scientific American. 



Incinerated Leaf of Deutzia — At the annual exhibition of the 

 Department of Microscopy of the Brooklyn Institute, U.S.A., 

 held in January, Mr. G. M. Hopkins, of the Scientific American, 

 exhibited a beautiful preparation of Deutzia leaf, which seems to 

 have the merit of novelty. The leaf was reduced to white ashes, 

 leaving the star-like hairs in situ. Some of the hairs were black- 



