1867.] 



made with a Rigid Spectroscope. 



7 



After carefully examining one or two positions in whicli the instru- 

 ment could be placed, Captain Mayne selected a place in Ms own cabin, 

 and explained to us that it was his intention to place the spectroscope 

 in charge of an intelligent young officer, Mr. Connor, the 2nd Master, 

 by whom the observations would be made ; but as the instrument neces- 

 sarily remained in Captain Mayne' s cabin, the observations would be 

 made generally in his presence, and under his immediate superin- 

 tendence. 



Captain Mayne and Mr. Connor shortly afterwards examined the 

 spectroscope at the rooms of the Eoyal Society, in the presence of Mr. 

 Stewart and myself, when they practised the mode of observing ; but, 

 in order to ensure the observations being subsequently made without 

 any bias as to obtaining particular results, no further explanation 

 was given to Captain Mayne or Mr. Connor, the latter being merely 

 requested day by day to note the result of his observations, and to 

 enter the same in printed forms with which he would be supplied, 

 Captain Mayne promising to forward the particulars to Captain 

 [Richards at his convenience. 



The form supplied was as follows : — 



Date. 



Latitude. 



Barometer. 



Temp, of 

 air. 



Temp, of 

 prisms. 



Eeading of 



micro- 

 meter for 

 D line. 



Remarks. 

















Mr. Browning, who constructed the instrument, took charge of it on 

 the 21st of August 1866, and proceeding to Woolwich placed it on board 

 the ' Nassau,' in the position which had been arranged by Captain 

 Mayne. 



On the 4th inst. I received a letter from Captain Mayne, of which 

 the following is an extract : — 



" H.M. Surveying Ship ' Nassau,' Straits of Magellan, 

 Feb. 16, 1867. 



" Mt dear Mr. GtASSIot, — As we are on our way to the Falkland 

 Isles, and my time will probably be fully occupied when we get there, 

 I write you a few lines to say that I am sending to the Hydrographer a 

 diagram of the observations of the spectroscope taken since we left 

 England ; with it I am sending a few remarks. I can only say that our 

 observations have been carefully taken, and I hope a discussion upon 

 them may throw some light upon the subject in which you and others 

 are so interested. Mr. Connor plotted the diagram with great care. 

 Usually the observations have been made by him, but I have taken 



