84 JAMES CLERK MAXWELL. [CHAP. IV. 



and a stroll on the estate in the afternoon ; or, if we 

 stayed at home, he would show his favourite books and 

 talk about them, till the evening closed with a chapter 

 and a prayer, which the old man read to the assembled 

 household. 



During the winter of 1846-47, James was unusually 

 delicate. He was often absent from school, and seems 

 not to have attended the meetings of the Societies. 

 But of these his father was sure to give him a faithful 

 report. He was certainly more than ever interested 

 in science. The two subjects which most engaged his 

 attention were magnetism and the polarisation of light. 

 He was fond of showing " Newton's rings " the chro- 

 matic effect produced by pressing lenses together 

 and of watching the changing hues on soap bubbles. 



In the spring of 1847 (somewhere in April) his 

 uncle, Mr. John Cay, whose scientific tastes have been 

 mentioned more than once above, took James and my- 

 self (with whom he chose to share all such delights) to 

 see Mr. Nicol, a friend of Sir David Brewster, and the 

 inventor of the polarising prism. 1 Even before this 

 James had been absorbed in " polarised light," work- 

 ing with Iceland spar, and twisting his head about to 

 see "Haidinger's Brushes" in the blue sky with his 

 naked eye. But this visit added a new and important 

 stimulus to his interest in these phenomena, and the 

 speculations to which they give rise. 2 



1 He lived in Inverleith Terrace, Edinburgh.. 



2 So far as I can recall the order in which his ideas on this sub- 

 ject were developed, the phenomena of complementary colours came 



