306 Royal Society : — 



begun at the red end, until on arrival at the region about b my atten- 

 tion was attracted by the fact that K 1657*1 by no means appeared 

 as the strong line depicted in Kirchhoffs map, Plate II. On ex- 

 amining this region carefully, I was surprised to find the colourless 

 lines shown in the diagram ; these lines, from want of a more ap- 

 propriate name, I shall call white lines (or spaces) ; they cannot ab- 

 solutely be described as bright lines, yet they closely resemble 

 threads of white floss silk held in the light. The spectroscope in 

 use, with the most convenient highest-power eyepiece, presents 

 images of about two thirds to seven ninths of those drawn in the 

 diagram ; the former are exaggerated by reckoning to agree with 

 KirchhofPs millimetre scale ; it will therefore be readily understood 

 that the white lines do not present striking objects in the spectro- 

 scope, especially about the time of sunset, when I happened first 

 to notice them ; they are best seen about noon, when their resem- 

 blance to threads of white floss silk is very close ; but once seen, 

 the lines in question can always be readily detected. So far as my 

 instrumental means permit, the wider line extends between K 

 1657*1 and K 1658*3 • more accurately speaking, it falls short of 

 the latter and rather underlies the former ; the narrower white line 

 is underneath K 1650*3, sensibly more of the former appearing 

 beyond the edge towards violet of the latter, which presents the 

 quaint look of a black line on a white surface enclosed in a green 

 band. These are the only white lines in the spectrum from extreme 

 red to ~F ; they are not bright (or reversed lines), so far as I have 

 had opportunity to judge. "Were they bright lines, the question 

 would arise, why these alone should be reversed at 6700 feet above 

 sea. Like the black lines the white lines grow dim and disappear 

 with the slit opened wide. As seen here, K 1657*1 is sensibly 

 weaker than K 1667*4, whereas Kirchhofl: assigns 5 b to the former 

 and only 3 a to the latter. 



March 12. — Joseph Dalton Hooker, C.B., President, in the Chair. 



The following communication was read : — 



" On a New Deep-sea Thermometer." By Henry Negretti and 

 Joseph "Warren Zambra. 



The Pellows of the Eoyal Society are perfectly aware of the 

 assistance afforded by Her Majesty's Government (at the request 

 of the Eoyal Society) for the purpose of deep-sea investigations, 

 and have been made acquainted with their results by the .Reports 

 of those investigations published in the * Proceedings of the Eoyal 

 Society 7 and by the interesting work of Professor "Wyville Thom- 

 son. Among other subjects, that of the temperature of the sea at 

 various depths, and on the bottom itself, is of the greatest import- 

 ance. The Fellows are also aware that for this purpose a peculiar 

 thermometer was and is used, having its bulb protected by an 

 outer bulb or casing, in order that its indications may not be viti- 

 ated by the pressure of the water at various depths, that pressure 

 being about 1 ton per square inch to every 800 fathoms. This 



