14 THE MICROSCOPE. Jan. 



the point of the whi-ker slightly, rack it down, and the diatom 

 will adhere to it. Raise it up, and place the slip on which it is 

 to be mounted on the stage. Th6 surface of this must, of course, 

 be ])repared with a gum solution, such as is described in the 

 text-books, and as the diatom touches it, it will leave the 

 whisker and adhere to the slip. This is not offered as a sub- 

 stitute f )r the mechanical finger entirely, but it is a simple 

 appliance that is easily made, and will be found useful many 

 times by those who are not fortunate enough to possess some- 

 thing better for the purpose. — Work. 



Stone Under the Microscope. — It is often held that the 

 best method of determining the probable durability of a build- 

 ing stone is to study its surface, or thin transparent slices, un- 

 der a microscope. This method of study in recent years has 

 been most fruitful in developing interesting and valuable knowl- 

 edge of a scientific and truly practical character. An examina- 

 tion of a section by means of the microscope will show not 

 merely the various substances which compose it, but also the 

 method according to which they are arranged, and by which 

 they are attached to one another. For example, pyrites is con- 

 sidered to be the enemy of the quarryman and constructor, 

 since it decomposes with ease and stains and discolors the rock. 

 Pyrites in sharp, well-defined crystals sometimes decomposes 

 with great difficulty. If a crystal or grain of pyrites is embed- 

 ded in soft, porous, light-colored sandstones, its presence will 

 certainly demonstrate itself by the black spot which will form 

 about it in the porous stone, and will permanently disfigure and 

 mar its beauty. If the same grain of pyrites is situ ited in or 

 near very hard, compact, non-absorbent stone, the constituent 

 minerals of which are not rifted or cracked, this grain of pyrites 

 may decompose and the products be washed awa}^ leaving the 

 stone untarnished. 



Higher Medical Education. — Rush Medical College will 

 hereafter require four years attendance at college from students 

 who begin the study of medicine. To encourage proper prelim- 

 inary study, graduates in arts and sciences from most colleges, 

 and graduates in pharmacy and dentistry from approved col- 

 leges will be graduated after an attendance on tlu'ee courses of 

 lectures. 



