1 862.] Professor Tyndall on Force. 527 



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WEEKLY EVENING MEETING, 



Friday, June 6, 1862. 



The Duke of Northumberland. K.G. F.R.S. President, 

 in the Chair. 



John Tyndall, Esq. F.R.S. 



PBOFESSOE OF NATURAL PHILOSOPHY, ROYAL INSTITCTION. 



On Force. 



The existence of the International Exhibition suggested to our Hono- 

 rary Secretary the idea of devoting the Friday evenings after Easter of 

 the present year to discourses on the various agencies on wliich the 

 material strength of England is based. He wished to make iron, coal, 

 cotton, and kindred matters, the subjects of these discourses ; opening 

 the series by a discourse on the Great Exhibition itself ; and he 

 wished me to finish the series by a discourse on *' Force " in general. 

 For some months I thought over the subject at intervals, and had 

 devised a plan of dealing with it; but three weeks ago I was induced 

 to swerve from this plan, for reasons which shall be made known 

 towards the conclusion of the discourse. 



We all have ideas n)ore or less distinct regarding force ; wc know 



