8 On the Atmospheric Lines of the Solar Spectrum. [June 16, 



aware that without suitable supervision the alterations could not be carried 

 out satisfactorily ; and in saying this, I make no doubt that Messrs. Trough- 

 ton and Simms wonld perform their part in their usual effective manner. I 

 already owe Mr. Huggins a considerable debt of gratitude for past superin- 

 tendence ; and his kindness on that occasion induces me to venture the hope 

 that he would undertake to direct such alterations as may be approved 

 of with despatch. 



25. Zodiacal light. — Every attention has been given to this subject, but 

 the only result obtained is, that no traces whatever of the zodiacal light 

 are visible here. I was on the watch in October and the early part of 

 November 1868. In April and May of 1869 my absence on duty at Dehra 

 prevented my devoting more than an occasional evening to the subject. 

 Last autumn, however, I gave it every attention, but all without seeing the 

 light. The following extract from my note-book, made the first morning 

 of my watching last winter, is a representative of all subsequent entries : — 



13th October, 1869. Mussoorie Observatory. — A beautifully clear 

 morning. Not a speck of cloud or mist to be seen. The horizon, S.S.E. 

 by S. to S.S.W., appears sharp and distinct, though some 90miles distant. 

 To the north, the snowy range, though some 60 miles away, appears hardly 

 a day's journey from this. The light is gradually increasing ; the red 

 rays now tinge the sky ; the sky itself brightens ; the highest peaks of the 

 snowy range are tipped with light ; the sun bursts over the hills as if in a 

 moment. All this has happened without any wings or rays preceding the 

 sun. In other words, no traces of the zodiacal light have appeared. 



26. The same, continued. — I watched for the light on the mornings of the 

 14th, 18th, 21st, 23rd, and 29th October, and on the 1st, 9th, and 15th No- 

 vember, 1869. On all these occasions the air and sky were beautifully clear. 

 Other dates of watching, under wrcfavourable circumstances, are excluded 

 from this list. Though no zodiacal light appeared to me at Mussoorie, it is 

 worthy of remark that Colonel Walker, while travelling by post across the 

 plains of Central India, saw a brilliant show of the light (as far as I can 

 reckon) between the 12th and 15th of November, 1869. Recently I watched 

 for the light on the evenings of the 11th, 12th, 13th, and 14th April, 18/0, 

 with the same results as before. 



27. The same, conclusion. — How far these facts supply a connecting-link 

 between the earth's atmosphere as a medium and the zodiacal light I leave for 

 the consideration of more competent authorities. The information may have 

 some special interest for Mr. Balfour Stewart, who, I learn from the monthly 

 notices of the Royal Astronomical Society, has given the subject some 

 attention. 



28. Actinometrical observations. — Discussion of these observations is 

 deferred until, with the assistance of Mr. W. H. Cole, M.A., I am able to 

 reduce and forward the results already obtained. The two actinometers 

 (Hodgkinson's) work capitally, and are in good order. Amongst other 

 observations, they have been compared with one another. Unfortunately 



