4 
16 THE AMERICAN MONTHLY (Jan 
be said that, according to this eminent authority, good rail 
steel consists of “ferrite,” or iron free from carbon, and “pear- 
lite,” which is a mixture of alternate bands of ferrite and 
“cementite,” the carbide corresponding to the formula Fe,C. 
The well developed pearlite with a conspicious banded 
structure is readily shown microscopically, and is character- 
istic of good rail steel. When, however, steel is hardened by 
“quenching,” pearlite is absent, and “martensite,” which con- 
sists of interlacing crystalline fibres without banded struc- 
ture, takes its place. Sir William Roberts-Austen says that 
“the presence of martensite in a rail should at once cause it 
to be viewed with extreme suspicion, as showing that the 
rail is too hard locally to be safe in use.” The broken rail at 
St. Neot’s showed an outside layer of martensite one hun- 
dredth of an inch thick. The report deals further with min- 
ute cracks found in this and other rails, and the enormous 
increase in liability to fracture occasioned thereby, and one 
conclusion drawn is that patches of martensite can be pro- 
duced in a rail, when in use, by local treating caused by 
skidding, followed by the rapid extraction of heat by the cold 
rail. It is thus evident that the microscope will prove to be 
an increasingly valuable means of studying the complex 
structure of steel. For this purpose and for the examination 
of alloys it is used, and already a quite voluminous literature 
is growing up around the subject. 
The Compound Microscope in Pharmacy. 
ALBERT SCHNEIDER, M. D., Ph., D. 
Compound Microscopes with objectives and oculars fair- 
ly well corrected for spherical and chromatic aberration, 
have been in use for nearly seventy-years, but it is only 
recently that they have been extensively employed in 
pharmaceutical practice, This is due to the fact that phar- 
macy as a science is of recent origin ; only within the last 
decade have the courses of instruction in the colleges of 
pharmacy been based upon scientific principles—at least 
