^{page 417 note *} By observations on Green CO on November 3, 4, and 5, it was ascertained that, after everything had been done at the place that could well be done to secure constancy of temperature in the bisulphide of carbon prisms employed, a slow fall of 1° Fahr. increased the Dispersive power of the collective train of prisms by 0·727 of a Revolution of the very coarse screw motion; or by close upon 10 inches on the surface of the recording barrel. The interval of time therefore between any two mutually dependent observations was, after that, made as short as possible.

^{page 417 note †} The diameter of the objectives was the same as in my earlier apparatus, viz., 2·25 inches, and the refracting faces of the prisms presented nearly the same breadth to the entering ray.

^{page 418 note *} The Members of the Committee are given thus—

Professor Dewar.

Dr Williamson.

Dr Marshall Watts.

Capt. W. de W. Abney, R.E.

Mr Stoney.

Professor Hartley.

Professor M'Leod.

Professor Carey Foster.

Professor A. K. Huntington.

Professor Emerson Reynolds.

Professor Reinold.

Professor Liveing.

Lord Rayleigh.

Dr Schuster, and

Mr W. Chandler Roberts, Secretary.

^{page 434 note *} From p. 14 of Messrs Angstrom and Thalen's Memoir. “Quant à l'observation de M. Atteield que l'oxyde de carbone donne le spectre ordinaire des carbures d'hydrogene, nous devons remarquer que cela ne s'accorde pas bien avec nos propres expériences.

“Dans un tube de Geissler, contenant de l'oxyde de carbone ou de l'acide carbonique, on peut certainement trouver des traces des spectres des carbures d'hydrogène, puisque le gas n'est jamais parfaitement sec.”

^{page 439 note *} The following note has been furnished to me:—“Herr Wessendonk prepared Siliceous gas with most scrupulous care and purity, without being able to obtain a trace of Silica lines, only CO bands over and over again, and more and more brilliant the purer the gas he used. Silica could never be found, in any quantity to speak of; so it could not have come out of the glass. SiH₂ and SiFl₂ were used (very easily prepared pure). CO was the only result he could possibly obtain. That, and always that.”

^{page 447 ntoe *} The manner in which the Red Hydrogen line comes into that Spectrum, is very striking, and I have not yet seen a good reason given for it.

^{page 452 note *} I thought, on the first discovery of 3 of these triplets, that they could he recognised in Angstrom's Normal Solar Map as dark Fraunhofer lines, but I delay now either affirming or refuting that idea, until I have made more satisfactory and exact observations on the Solar Spectrum itself.

^{page 454 note *} This was merely the raw record-slip taken at the Instrument, in the manner which I specially arranged for all the Spectra described in this paper.—C. P. S.

^{page 455 note *} These very ingenious card strips of Prof. Herschel's, being unsuited to book-illustration,—it occurred to me, to prepare Plate LXXVIII., including them both and the manner of working them, but in one statical view. This Plate afterwards had his approval, though with a proviso touching ideal accuracy, which he has touched on in Appendix II. page 43.—C. P. S.