Mr Sang^s Analysis of the Vibration of Wires. 819 



analysis, and that it may ultimately lead to a knowledge of the 

 more intricate acoustic phenomena, I may be pardoned the 

 having pushed to such an extent a mere exercise for amuse- 

 ment. 



The whole of these curves can be delineated on paper by 

 means of a very simple apparatus ; of this I intend to give a 

 description at an after time ; and, at least, this benefit has arisen 

 from the investigation, that it has led to the invention of an ef- 

 fective parabola and ellipto-graph, suited to the description of 

 minute curves. 



To those who are conversant with such investigations, it will 

 at once appear that a similar analysis would apply to the mo- 

 tion of the mast-head of a ship, and that that point describes, 

 when the vessel both pitches and rolls, some one of these tra- 

 jectories. 



I have next to proceed to the investigation of the nature of 



curves described by the extremities of bent wires ; but this I 



shall defer till another opportunity. 



32, St Andrew's Squaee, \ 

 October 15. 1831. I 



On the Uniform Permeability of all known Substances to the 

 Magnetic Influence, and the Application of the fact in En- 

 gineering and Mining, for the Determination of the Thick- 

 ness of Solid Substances not otherwise Measurable. By the 

 Rev. William Scoresby, F. R. S. Lond. & Edin., Corres- 

 pondent of the Institute of France, &c. &c. Communicated 

 by the Author. 



\Lh£ general permeability of solid substances by the magne- 

 tic influence, is a fact so extensively accredited, as to be acted 

 upon by all practical men who make use of the compass ; but 

 I am not aware of any series of experiments having been pro- 

 fessedly undertaken, to ascertain whether this permeability be 

 at once universal, and uninterrupted or unlimited. The re- 

 sults of experiments undertaken with the view of determining 

 these particulars, will, I apprehend, go far to shew, that, of a 

 vast number and variety of bodies in which experiments have 

 yet been made, not even excepting iron in all its states, condi- 



