850 RECOBD OF CURRENT RESEARCHES RELATING TO 



Mr. Eutley laimself says : * — In the case of very soft rocks, such 

 as tuffs, clays, &c., useful information may sometimes be acquired 

 by washing to pieces fragments of the rock ; in this way a fine mud 

 and often numerous minute crystals and organisms may be procured. 

 The best aj^paratus for effecting this gradual washing is a conical 

 glass about 9 or 10 inches high, across the mouth of which a cross- 

 bar of metal or wood is fixed. A little hole drilled in the centre of 

 the bar receives the tube of a small thistle-headed glass funnel. 

 Roughly broken fragments of the rock should be placed in the 

 bottom of the conical glass, and the apparatus set beneath a tap, 

 from which a stream of water is continually allowed to run into the 

 mouth of the funnel, the overflow trickling down the sides of the 

 glass, which should consequently be placed in a sink. In this 

 manner a constant current is kept up, and the fragments at the 

 bottom of the glass are continually turned over, agitated, rubbed 

 against one another, and gradually disintegrated. This action should 

 be kept up, often for many days, until a considerable amount of dis- 

 integrated matter has accumulated. Samples should then be taken 

 out by means of a pipette and examined under the Microscope. 



When the observer wishes to mount either such materials or fine 

 scaly, powdery, or minutely crystallized minerals, the best method is 

 to spread a little of the substance on a glass slide, moisten the powder 

 with a drop of turpentine, and then add a droj) of Canada balsam, and 

 cover in the usual manner. If the attempt be made to mount 

 such substances directly in balsam, without the intervention of 

 turpentine or some kindred medium, air-bubbles are almost certain to 

 be included in the preparation. 



Lenses for Petrographical Work. — Mr. Melville Attwood, in a 

 paper read before the San Francisco Microscopical Society, quotes the 

 following passage from Mr. Frank Eutley's book on ' The Study of 

 Eocks' t : " There is, however, a disadvantage attending the use of lenses 

 when they are applied to the examination of rocks. This lies in the 

 difficulty experienced by the observer when he attempts to examine 

 the streak of minerals under the lens, especially when the minerals 

 occur in very minute crystals or patches, as it is scarcely possible to 

 ■hold a specimen, with a lens over it in focus, in one baud, and to 

 Ivork with a knife in the other. Laying the specimen on a table, 

 and using a lens in one hand and a knife in the other, is a most 

 Unsatisfactory process ; while the use of a lens fixed on an adjusting 

 stand is scarcely better. To obviate this difficulty, the author has 

 devised a small lens with a clip, which can be worn on the nose like 

 an eye-glass, and both hands are then at liberty — the one to hold the 

 fepecimen firmly, the other to use the knife or graver. This clip-lens 

 is moreover better than a watchmaker's eye-glass, because it entails 

 no muscular effort to keep it in place. It is better to have the lens 

 mounted in a horn than in a metal rim as it is less heavy and con- 

 sequently less liable to be accidentally shifted or displaced by the 

 inclination of the head." 



* F. Rutley's ' Study of Eocks^',(Svo, London, 1S79), p. 73. 

 t Il'id., p. 44. 



