THE AMERICA^ MONTHLY [July 



Fibres. — Vegetable fibres may be distinguished from 

 animal fibres by treatment with iodine and dilute sul- 

 phuric acid. The former take a characteristic color,either 

 yellow or blue, while the latter do not. The re agents 

 should be prepared as follows : — Dissolve one part of 

 potassium iodide in one hundred parts of distilled water, 

 and add an excess of pure iodine, so that the solution 

 shall always remain saturated. Mix one part of distill- 

 ed water with three parts of sulphuric acid, and, when 

 cool, add two parts of Price's glycerine. Both re-agents 

 should be kept in glass-stoppered bottles, and as they are 

 liable to change they should be occasionally tested on 

 known fibres. These re-agents, applied under the micro- 

 scope, afford a means of determining the species from 

 which the fibre is derived. To do this, some cells should 

 be separated, extended on a glass slip, and slightly moist- 

 ened with glycerine. The length and breadth may then 

 be determined with a micrometer, and note should be 

 made, at this stage, of the shape and degree of taper of 

 the cells. Allow a small drop of the iodine to flow under 

 the cover, removing any surplus with blotting paper. As 

 soon as the iodine has penetrated, apply the sulphuric 

 acid in the same way, carefully watch the results, and 

 compare them with the action of the re-agents on known 

 fibres. 



Section-lifter. — A cheap and effective section-lifter 

 may be made by hammering out flat the end of a copper 

 wire of one-eighth inch in diameter and four inches long. 

 The hammering should be done on a smooth iron, and 

 when it is of the requisite width it may be trimmed with 

 a pair of scissors and smoothed on a whetstone. 



Rock Powder. — Miss Catherine Raisin writes: "On 

 certain structures formed in the drying of a fluid with 

 particles in suspension," in which she described the many 

 interesting forms that the powders of various rocks ex- 

 hibit when mounted in water and dried. These forms are 



