THE BIRKBECK INSTITUTION. 239 



very cheap and very bad, but they were liked by my 

 illustrious friend, and were doubtless to him a source of 

 comfort. Dr. Debus, the late distinguished professor of 

 chemistry at the Eoyal Naval College, Greenwich, was 

 Bunsen's laboratory assistant at this time, and to him I 

 was indebted for some lessons in blowpipe chemistry. 

 Bunsen afterwards took me under his own charge, giving 

 me Icelandic trachytes to analyse, and other work. 

 Besides being a chemist, he was a profound physicist. 

 His celebrated * Publicum ' on electro-chemistry, to 

 which we all looked forward as a treat of the highest 

 kind, was physical from beginning to end. He was the 

 intimate friend of W. Weber of Gottingen, and was well 

 acquainted with the labours of that great electrician. 

 Breaking ground in frictional electricity, he passed on 

 to the phenomena and theory of the Voltaic pile. He 

 was a great upholder of the famous Contact Theory, 

 which had many supporters in Germany at the time, one 

 of the foremost of these being the genial-minded Kohl- 

 rausch. This theory, as you are well aware, has under- 

 gone profound modifications. There are, no doubt, 

 eminent philosophers amongst us who would pronounce 

 the theory, in its first form, unthinkable, inasmuch as 

 it implied the creation of force out of nothing. But 

 the fact that some of the most celebrated scientific 

 men in the world, with the illustrious Volta himself as 

 their leader, accepted and saw nothing incongruous in 

 the theory, shows how ' unthinkability ' depends upon 

 the state of our knowledge. The laws of Ohm were ex- 

 pounded with great completeness by Bunsen. Various 

 modes of electric measurement were illustrated ; the 

 electric light from the carbon battery, invented by 

 himself, was introduced, the electric telegraph was ex- 

 plained, Steinheil's researches in regard to the ' earth 

 circuit ' were developed ; and it was in these lectures 



