38 THE MICROSCOPICAL NEWS. 
drawings which accompany the work of M. Pfitzer are in part 
diagrammatic. j 
I have sought to obtain, by a different process, sections of this 
diatom, so as to give a more faithful representation. I have chosen 
a good sample of Franzensbad earth, which our colleague, M. 
Mauler, has been good enough to procure for me, containing small 
agglomerations more coherent than the rest of the mass. These 
were boiled in Canada balsam to harden them. After this treat- 
ment they were then ground down by means of emery as other 
mineral and rock sections. 
This method has the inconvenience of necessitating the employ- 
ment of heat to fix the ground fragment to the glass slip. __In per- 
forming this operation it is necessary to act with caution and 
rapidity, to avoid softening the balsam which binds the diatoms 
fr 
Fig. 14. 
together so as not to displace or break them. I have thus obtained 
thin plates of a centimetre square, containing hundreds of sections 
of the diatoms perpendicular to the main axis of the frustule. 
Contrary to my expectations, not a single section gave me a clear 
image of the raphe. These preparations were always irreproachable 
and of extreme thinness, in spite of the friability of the sub- 
stance. Where the raphe and connectives were found the sections 
had a hazy mutilated appearance, which rendered observations very 
difficult. I believe I have sometimes seen the thickness of the 
valve traversed by a broken line, similar to that shown by M. 
Pfitzer ; sometimes this line was more or less oblique. 
These appearances are doubtless due to the fact that the balsam, 
used to consolidate the frustules, does not penetrate into the 
interior of them: They remain then empty, and their finest details 
were not sufficiently supported, and so could not resist the grinding 
