[28] 



H fiftetbot) of flDafting an& flDounting Zmne- 

 parent IRocft^^Sectione for flDicroscopic 



By John Smith. 



THE following method of making and mounting transparent 

 Rock-sections for the microscope, was taught me several 

 years ago by the late Mr. Arthur Pratt, of Glasgow. And, 

 with a few exceptions, which will be noted, the method I use 

 is essentially that followed by Mr. Pratt. 



The first step is of course to get a suitable piece of rock, say, a 

 fragment of Trap or Basalt. 



This should be broken as thin as possible, and to do this, 

 having struck off a fragment from the parent rock, or boulder, 

 take it between the fingers and thumb of the left hand. Hold one 

 edge on the rock from which it was struck, or any hard stone 

 which may be convenient, and strike it a sharp blow with the 

 hammer, fair on the opposite edge. If this is well done thin 

 fragments, about one-eighth of an inch thick, will fly off. 



These fragments ought to be rough-hewn, on the spot, so long 

 as there is plenty of material to work from, and for this purpose I 

 use a pair of cutting nippers such as are used for cutting wire. 

 With a little practice, any one will soon become expert in using 

 them. Take a thin fragment of the rock in the left hand, and 

 with the nippers work round it, clipping off the superfluous angles 

 until a disc of about seven-eighths of an inch in diameter is formed. 

 With a little experience this can be done in less than a minute. 

 My practice is to take four such discs, of each kind of rock 

 from which I wish to make sections ; two to ensure getting a 

 finished section, and two to meet the requirements of friends. 



I also take a thin piece of the rock one inch and a quarter 

 square, or thereabouts, as a cabinet specimen, and for comparison 

 with the finished section. This specimen should, if possible, 

 show a weather-worn face, although it is not always possible to get 

 a specimen in this state, especially if it is taken from a mine; or 



