vi.] PROFESSORIAL LIFE. 147 



by a pretty violent heat ; but it was far too insensible to 

 be of the slightest use. It was, I think, iodide of silver. 

 Is the impression on yours permanent, and would you 

 allow me to try a small piece of it ? . . . Have you ever 

 applied photography to the beautiful figures of polariza- 

 tion and diffraction ? The only experiment I ever made 

 on the subject which I have purposely avoided spending 

 i;iv time upon, seeing that it is in much better hands- 



to fix the splendid image of calc spar rings nn<l 

 brushes by solar light, and to my surprise I wholly failed. 

 Perhaps the calc spars had absorbed the chemical rays ; 

 but at all events my experiment, being but once made 

 and by inexperienced hands, was not worth much/ 



But much as his experiments and discoveries filled 

 his time and attention, they still left room for graver 

 thoughts. 



The following extract from his journal was written just 

 before he entered on the work of the session 1839-40 : 



' THE DEAJ* HOUSE, Oct. 20th, 1839. 



' Five years and a half have elapsed since the last pages 

 11 ! AYhat a chasm in anticipation! What a 

 span in retrospect! I thank Almighty God that if any 

 one change more than another has characterized my 

 1. it i< Mil approximation to the fulfilment of the 

 i expressed in t lie last sentence. I yearly feel a greater 

 -s to die, and become more familiarized with the 

 idea. I wish that I could impute this to an increasing 

 ss for such a change ; it arises, I am perfectly 

 aware, fully more from the experience of satiety even 

 in the more intellectual earthly gratifications. . . . Yet 

 my grounds of calm antieipation of the future have 

 y in some respects greatly improved in these 

 irs. I have a far more settled and reasonable de- 

 pendence on the atonement of Jesus Christ, a doctrine of 

 which God's grace has within these few years revealed to 

 me the full importance, as a ground of h<>]>e and guide 

 of action. I am now about to cehl.iate tin i.nih anni- 



L 2 



