104 



Lieut. J. HerscheFs Account of the [Nov. 19, 



municated by the Right Hon. Lord Stanley, F.R.S. Received 

 October 8, 1868. (See page 81.) 



VII. " Further Particulars of the Swedish Arctic Expedition ." In a 

 Letter addressed to the President, by Professor Nordenskiold. 

 Communicated by the President. Received October 15, 1868. 

 (See page 91.) 



VIII. " Notice of an Observation of the Spectrum of a Solar Promi- 

 nence." By J. N. Lockyer, Esq., in a Letter to the Secretary. 

 Communicated by Dr. Sharpey. Received October 21, 1868. 

 (See page 91.) 



IX. " On a New Series of Chemical Reactions produced by Light." 

 By John Tyndall, LL.D., F.R.S., &c. Received October 24, 

 1868. (See page 92.) 



X. " Account of the Solar Eclipse of 1868, as seen at Jamkandi in 



the Bombay Presidency." By Lieut. J. Herschel, R.E. Com- 

 municated by Prof. G, G. Stokes, Sec. R.S. Received October 

 19, 1868. 



To the President, Council, and Fellows of the Royal Society. 

 Gentlemen, — The time has arrived when I must offer for your accept- 

 ance a connected report of the employment of the instruments intrusted to 

 me for the special purpose of observing the late solar eclipse. 



1 . Plan of this Report. 

 In framing this Report I propose in the first place to describe those in- 

 struments sufficiently in detail to render unnecessary such explanations as 

 would otherwise be required in the course of my narrative, and then to 

 show the circumstances which preceded their actual employment on that 

 occasion. 



2. Description of Telescope and clockwork. 

 The principal instrument is an equatorially mounted telescope, with a 

 lens of 5 inches aperture and 62 inches focal length. The mounting is 

 adapted to any latitude (except very low and very high ones), the polar 

 axis being a moveable tangent to the circular-arched roof of the chamber con- 

 taining the clockwork. The latter, as well as the rest of the instrument, is by 

 Messrs. Cooke and Sons, of York, and is, as I understood from Mr. Cooke, of a 

 somewhat novel description. I have not examined the mechanism closely, 

 and therefore cannot describe it very accurately ; but I believe the peculiarity 

 consists in the maintenance of continuous motion in a fan-wheel, regulated by 

 a pendulum time-keeper acted on through a remontoir escapement, whereby 

 the irregularity of the surplus energy of the driving-weight, while it is pre- 

 vented by the latter from interfering with the time-keeper at all, is modi- 

 fied in its action on the tube by the former. The mean rate of motion is 



