THE 



MONTHLY MICROSCOPICAL JOURNAL. 



JUNE 1, 1874. 



I. — On certain Beaded Silica Films Artijicially Formed. 



By Henry J. Slack, F.G.S., Sec. E.M.S. 



(Bead be/ore tlie Royal Microscopical Society, May 6, 1874.) 



Plate LXIII., and upper part of LXIV. 



On a former occasion the writer called the attention of the Society 

 to the large number and variety of beaded patterns that could be 

 obtained by making the artificial diatoms of Max Schultze. In 

 forming these objects silicic fluoride gas is allowed to come into 

 contact in its nascent state, with cotton filaments moistened with 

 water. The result is a deposition of silica in the shape of irre- 

 gular vesicles, the waUs of which exhibit beaded structures in 

 definite patterns ; the beads in different, and in similar patterns, 

 varying greatly in size ; and many of the patterns being composed 

 of two or more sized beads, usually symmetrically arranged. 



When the silica in this gaseous state comes into contact with 

 water, in a mass instead of being distributed in finely divided por- 

 tions adhering to absorbent filaments, it is deposited in amorphous 

 particles, which, when magnified, exhibit numerous flaws, but no 

 regular structure. It seems as if the passage from the gaseous to 

 the solid state was too sudden and violent for any definite pattern to 

 be formed. In hke manner when silica is precipitated from its 

 alkaline salts, or " water glasses," dissolved in water, only angular 

 amorphous particles are obtained, and a similar result follows the 

 gradual drying up of a dialyzed solution of silica in water, as the 



DESCRIPTION OF PLATE LXIII., and upper half of PLATE LXIV. 



Figs. 1 and 2. — Cellular aspects of films X with Powell and Lealand's |th 

 objective. 



Figs. 3, 4, ."5. — Organic forms in some films — the framework of the cells 

 probably composed of minute coalescing beads. They were most favourably 

 situated for resolution. 



Fig. 6. — Upper figure, branching fungoid-looking threads common on films ; 

 lower figure, similar threads resolved into beads. 



Fig. 7. — Forms like 6 frequently found on thin films as if sprouting from them, 

 highly magnified with Powell and Lealand's i\th.. 



Fig. 8. — Remarkable specimen of the same. 



The above figures are copied from drawings of the objects made by Dr. Anthony, 

 F.R.M.S., and kindly presented to the author. 



VOL. XI. T 



