THE FORMS OF WATER 



IN 



CLOUDS AND RIVERS, ICE AND GLACIERS, 



BY 



JOHN TYNDALL, LL.D., F.R.S., 



PROFESSOR OF NATURAL PHILOSOPHY IN THE ROYAL INSTITUTION, LONDON. 



WITH NINETEEN ILLUSTRATIONS DRAWN UNDER THE DIRECTION 



OF THE AUTHOR. 



PREFACE TO THE FOURTH EDITION. 



AT a meeting of the Managers of the Royal 

 Institution held on December 12th, 1825, 

 " the Committee appointed to consider what 

 lectures should be delivered in the Institu- 

 tion in the next session," reported " that they 

 had consulted Mr. Furaday on the subject of 

 engaging him to take a part in the juvenile 

 lectures proposed to be given during the 

 Christmas and Easter recesses, and they 

 found his avocations were such that it 

 Would be exceedingly inconvenient for him 

 to engage in such lectures." 



At a general monthly meeting of the mem- 

 bers of the Royal Institution, held on Do- 

 cember 4th, 1826, the Managers reported 

 " that they had engaged Mr. \Vallis to deliver 

 a course of lectures on Astronomy, adapted 

 to a juvenile auditory, during the Christmas 

 vacation." 



In a report dated April 16th, 1827, the 

 Board of Visitors express " their satisfaction 

 at finding that the plan of juvenile courses 

 of lectures has been resorted to. They feel 

 sure that the influence of the Institution can- 

 not be extended too far, and the system of 

 nstructing the younger portion of the com- 

 munity is one of the most effective means 

 Which the Institution possesses foi the diffu- 

 :2on of science." 



Faraday's holding aloof was but tempo- 



IS", for at Christmas. 1827, we iiud him 



giving a " Course of Six Elementary Lectures 

 on Chemistr}', adapted tc a Juvenile Audi- 

 tory."* 



The Easter lectures were soon abandoned ; 

 but from the date here referred to to the pres- 

 ent time the Christmas lectures have been a 

 marked feature of the Royal Institution. 



In 1871 it fell to my lot'to give one of these 

 courses. I had been frequently invited to 

 write on Glaciers in encyclopedias, journals, 

 and magazines, but had always declined to 

 do so. I had also abstained from making 

 them the subject of a course of "lectures, 

 wishing to take no advantage of my position 

 here, and indeed to avoid writing a line or 

 uttering a sentence on the subject for whicb 

 1 could not be held personally responsible. 

 In view of the discussions which the subject 

 had provoked, I thought this the fairest 

 course. 



But, in 1871, the time (I imagined) had 

 come, when, without risk of offence, I might 

 tell our young people something about the 

 labors of those who had unravelled for their 

 instruction the various problems of the ice- 

 world. My lamented friend and ever-helpful 

 counsellor, Dr. Bence Jones, thought the 

 subject a good one, and accordingly it was 

 chosen. Strong in my sympathy with youth, 

 and remembering the damage done by defec- 

 tive exposition to my own young mind, I 

 sought, to the best of my abiiity, to confer 

 upon these lectures clearness, thoroughness, 



