^{page 548 note *} Two Processes for Silicon, by Dr Samuel Brown. Edinburgh: Adam and Charles Black. 1843.

^{page 549 note *} The atomic weight of silicon, according to Berzelius, is 22·22; that of silica 46·22.

^{page 551 note *} A platina crucible was used at the risk of destroying it by the fusion of the silver; porcelain being objectionable as containing silica.

^{page 551 note †} In the only experiment of which the exact quantities are recorded, 17·9 grs. of the brown powder (diparacyanide of silver?) gave of silica 0·5 gr.

^{page 551 note ‡} Transactions of the Royal Society of Edinburgh, vol. xv. p. 244.

^{page 552 note *} Transactions of the Royal Society of Edinburgh, vol. xv. p. 245.

^{page 553 note *} Transactions of the Royal Society of Edinburgh, vol. xv. p. 174.

^{page 553 note †} Ibid. pp. 238, 239.

^{page 554 note *} Trans. of Royal Soc., vol. xv. p. 168.

^{page 555 note *} Transactions of the Royal Society, vol. xv. p. 236. The numbers, we suppose, have here been accidentally inverted, an 11th being more than a 12th.

^{page 556 note *} Transactions of Royal Society, vol. xv. p. 233.

^{page 557 note *} When our paper was read, another repetition of this experiment was in progress, which has since been completed. Twenty grains of purified paracyanogen were heated in an iron crucible for three days. On examination, the powder was found so little changed in bulk and colour, that the lid of the crucible was replaced, and the heating continued for three days more. A very pale brown powder was left, amounting to 0·5 gr., which, when fused with carbonate of potass, left a trace of what appeared to be silica.

^{page 558 note *} An abstract of Mr Knox's paper, which has not, so far as we know, yet been published, will be found in the London and Edinburgh Philosophical Magazine for 1843.

^{page 558 note †} Trans, of Royal Soc., vol. xv. p. 175.

^{page 558 note ‡} We offer no opinion as to the constitution of paracyanogen. By the substance which we so designate, we mean the black powder obtained by heating cyanide of mercury; and in speaking of its reversion into cyanogen, we purposely use the language of Dr Brown, who supposes it to be a combination of two atoms of cyanogen.

^{page 559 note *} This fact has been already noticed by Professor Johnston, Transactions of the Royal Soc. of Edinburgh, vol. xiv. p. 37; and by Messrs Smith and Brett, London and Edinburgh Philosophical Magazine, vol. xx. p. 29; but we have mentioned our experiment particularly, because it was made with paracyanogen purified in the way already mentioned, and the quantity of cyanide of silver produced was ascertained.