Chap. 46.] 
vabtolts kinds of niteum. 
515 
a charcoal fire.'^ When substances'^^ are wanted to keep, they 
employ this last kind of nitrum. In Egypt there are also nitre- 
beds, the produce of which is red, owing to the colour of the 
earth in the same locality. Froth of nitrum, a substance 
held in very high esteem, could only be made, according to the 
ancients, when dews had fallen ; the pits being at the moment 
saturated with nitrum, but not having arrived at the point of 
yielding it. On the other hand, again, when the pits were in 
full activity, no froth would form, it was said, even though 
dews should fall. Others, again, have attributed the formation 
of this last substance to the fermentation of the heaps of 
nitrum. In a succeeding age, the medical men, speaking of it 
under the name of aphronitrum,''^^ have stated that it was 
collected in Asia, where it was to be found oozing from the 
soft sides of certain mines — the name given to which was 
*^ colyces"^^ — and that it was then dried in the sun. The very 
best is thought to be that which comes from Lydia ; the test of 
its genuineness being its extreme lightness, its friability, and 
its colour, which should be almost a full purple. This last is 
imported in tablets, while that of Egypt comes enclosed in 
quentes in carbonibus." This passage Beckmann pronounces to be one of 
the darkest parts in the history of nitrum. See Vol. II. p. 502. He is of 
opinion that not improbably the result here obtained would be, liver of 
sulphur, which when it cools is hard, but soon becomes moist when ex- 
posed to the air. Dalechamps, it would appear, explains the whole of this 
passage as applicable to glazing ; but in such case, as Beckmann observes, 
the nitrum could serve only as a flux. Michaelis suggests that the vessels 
here mentioned, were cut, not for real use, but merely for ornament, in the 
same manner as they are still made, occasionally, from rock-salt. 
The mention of nitrum, sulphur, and charcoal, probably the three 
ingredients of gunpowder, in such close proximity, is somewhat curious. 
" Quae " seems a preferable reading to quos." 
^0 " Spuma nitri." An accidental property, Beckmann says, of the 
SLime salt that has been previously called Chalastricum," *' Halmyrax," 
Aphronitrum," and " Agrion." In his opinion, " the ancients were ac- 
quainted with no other than native nitrum, which they called artiJiUal, 
only when it required a little more trouble and art to obtain it.*^ — Hist. 
Inv. Vol. II. p. 502. Jiohny Ed. 
^1 *' Froth of nitre." Ajasson identifies this with hydro -carbonate of 
soda. 
^'^ Supposed by Hardouin to be derived from the Greek koXikuc., round 
cakes;" owing to the peculiar form of the pieces of rock by which the 
aphronitrum was produced. The reading, however, is very doubtful. 
Sillig, from Photius, suggests that it should be ** scolecas." 
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