16 Messrs. Faraday and Lyell on 



where the glacier is most dislocated, and not where it is most 

 compact, because it is in those places that I conceive the sli- 

 ding of one part past another to take place. That such is the 

 case in many places is as unquestionable as the continuity of 

 the motion observed by Prof. Forbes. It must not be sup- 

 posed, however, that I reject the notion of ice having a certain 

 degree of plasticitj/ and Jlexihility'^. It would be absurd for 

 any one to do so who has witnessed how the glacier de 

 I'Echaud and the glacier du Tacul form, by their union, the 

 Mer de Glace, and the glaciers of Finsteraar and Lauteraar 

 form that of the Lower Aar. But I believe that these proper- 

 ties are only developed in glacial ice to any considerable ex- 

 tent, by the enormous forces to which certain portions of a 

 glacier are subjected ; and I contend that this plasticity is not 

 such that the mechanism of glacial motion can be correctly 

 represented by that of a semifluid or viscous substance. But 

 I must reserve the subject of the mechanism of glacial motion 

 for my next communication. 



Your obedient Servant, 

 Cambridge, November 19, 1844. W. HoPKlNS. 



II. lleport from Messrs. Faraday and Lyell to the Rt. Hon. 

 Sir James Graham, Bart., Secretary of State for the Ho?ne 

 Department, on the subject of' the Explosion at the Hasx<cell 

 Collieries, and on the means of preventing similar accidefitsf. 



To the Right Honourable Sir James Graham, Bart., Sfc. Sfc. 

 Sir, 

 ILIAVING, in our former letter, expressed our entire con- 

 ■*- -■■ currence in the verdict of the jury, which exonerated the 

 proprietors of the Haswell Colliery from any blame in con- 

 nexion with the late fatal accident (September -28, 184!4), we 



* The terms plastic, flexible, viscous, semifluid, &c., appear to have been 

 used by Prof. Forbes too indiscriminately, as if they were convertible terms, 

 which is very far from being the case. The application of the two latter 

 terms to a hard mass, like glacial ice, capable of supporting itself when 

 bounded by a free vertical section of a height at least a hundred, and 

 perhaps many hundred feet, I cannot but regard as a departure from all 

 propriety of established language. 



•f [To this Report, which has been published by the Home Office with il- 

 lustrative plans, and which has been obligingly communicated to us by the 

 Authors, the following notice is prefixed : — 



"Home Office, Nov. 13th, 1844. 



"On the occasion of the late fatal Explosion in the Colliery at Haswell, 

 Messrs. Lyell and Faraday were appointed by Sir James Graham to attend 

 at the Coroner's Inquest, for the purpose of affording any information in 

 their power, and for reporting also whether any means could be suggested 

 for preventing similar accidents. The following Report has been received 

 from those Gentlemen."] 



