PREFATORY NOTE 



RECENT PROGRESS AND PRESENT ASPECT OF 

 THE THEORY OF GLACIERS. 



IN 1850, Mr. Faraday delivered a lecture at the Royal In- 

 stitution on certain properties of water, and more especially of 

 water in the act of freezing. This lecture was never (I be- 

 lieve) published by authority. But an abstract of it appeared 

 in the Athenaeum Journal for June 15, 1850,* and also in the 

 Literary Gazette. In this brief and imperfect summary of what 

 must evidently have been an interesting and suggestive dis- 

 course, it is stated, that if a film of water be enclosed between 

 two plates of ice. even at a thawing temperature, the film of 

 water is frozen, and the plates of ice cohere ; and also that 

 damp snow becomes, by the same process, compacted into a 

 snow-ball, which will not occur if the snow is dry and hard 

 frozen. 



These facts appear to have excited little notice, until atten- 

 tion was called to them by Dr. Tyndall in a lecture, also delivered 

 at the Royal Institution, on the 23d January 1857. He gave to 

 the phenomenon the name of regelation. He applied it to ex- 

 plain the observation, that portions of ice crushed in a mould 

 under Bramah's press may assume new and compact forms with- 



* Keprinted in the Second Appendix to the present volume. 

 b 



