^SLlKTim^] Crystals in Blow-pijpe Beads. 349 
IV. — On Crystals enclosed in Blow-pipe Beads. 
By H. C. SoRBY, F.K.S., &c. 
Plate XYII. (lower portion). 
At the soiree of tlie Koyal Society on Marcli 6, by the kind assist- 
ance of my friend Mr. Wm. Baker, I exhibited a number of blow- 
pipe beads enclosing various crystals of such extreme beauty as 
mere microscopical objects, that probably some account of them 
may be interesting, independent of their connection with chemistry 
and mineralogy. 
It has long been known that blow-pipe beads often become 
opaque on flaming ; and Emerson * showed that, by proper mani- 
pulation, well-formed crystals can be produced in them, and 
recognized by their characteristic forms when magnified. Kose f 
described very interesting results thus obtained in the case of 
titanic acid ; and Captain Koss has published several papers in the 
' Chemical News,' t in which he gives the results obtained by blow- 
ing out the beads into thin vesicles, exhibiting minute characteristic 
crystals. My method differs materially from those described by the 
above-named authors. I use borax as the solvent, and, if requisite, 
add various reagents to produce, as it were, precipitates of charac- 
teristic crystalline form. By keeping the supersaturated fused bead 
over the flame, crystals may be obtained in cases where, according to 
Emerson, nothing satisfactory results from mere flaming ; and the 
addition of various reagents adds greatly to our resources in the 
case of earths variously mixed or combined with mineral acids. 
It is not my intention to enter now into the purely chemical part 
of the subject, or to show its apphcation to mineralogy. I shall 
merely give a short account of some specimens thus prepared, which 
may be of interest as microscopical objects of remarkable character. 
Many are good illustrations of the manner in which crystals grow 
up from simple nuclei to complicated forms of extreme beauty ; and 
it is very instructive to see how the definite secondary planes of the 
crystals, viewed as a whole, are produced by the regularly gradu- 
ated growth of numerous small crystals symmetrically deposited. 
This is sometimes so striking (see Figs. 3 and 4), as to lead me to 
hope that further study may throw important light on the cause 
of the production of secondary crystalline forms. 
* * Proceedings of the American Academy,' 1866, vol. vi., p. 476. 
t Berlin Acad. Bericht, 1867, pp. 129, 450. 
i Vols, xvi., p. 370 ; xvii., pp. 35, 63, 82, 87, and 107. 
2 B 2 
