76 Scientific Notices — Miscellaneous. [July, 



motion to be wholly produced by the centre of gravity of the 

 piece of camphor, and of the fluid displaced by it not being 

 in the same vertical line. If that were so, an irregular piece 

 of any substance capable of floating on water should, under 

 the same circumstances, exhibit the same phenomena as a 

 piece of camphor, which is not the case. Another, and co- 

 operating cause must, therefore, be looked for ; and there seems 

 no reason to doubt that it is correctly assigned in M. Biot's 

 abstract. Yours, F. B. 



9. Improvement in Clocks. 



The public papers, sometime since, contained information of 

 an improvement in timekeepers, invented by Mr. Dyer, of this 

 city. We hope hereafter to furnish our readers with a more 

 particular account of this invention than is contained in the 

 following brief notice : — 



The most important feature in this improvement consists 

 in the application of the spiral teeth to the wheel-work of 

 clocks, and in this the pinion is reduced to a single tooth. By 

 this happy idea, Mr. Dyer has greatly reduced the wheel-work 

 necessary to a clock, and the friction is diminished in a still 

 greater degree ; as all who are acquainted with the spiral gear- 

 ing are aware that the point of contact, between two wheels 

 with spiral-teeth, always coincides with the line of centres. 

 Mr. Dyer has also contrived a very ingenious method of sus- 

 pending the pendulum, in place of the spring, or knife-edge 

 suspension. This method is to hang the mass constituting the 

 pendulum to a plane, the under surface of which rolls at every 

 oscillation upon a fixed convex body. He proposes to give 

 such a curve to the convex surface, that the pendulum, in 

 vibrating, shall be accelerated at every moment of its descent 

 by a force proportional to the arch between it and the lowest 

 point ; this condition being required to render the vibrations 

 isochronal. Mr. Dyer has not yet demonstrated the curve 

 necessary to obtain this result ; but from the constant variation 

 of the centre of oscillation, in a pendulum suspended in the 

 above method, the cycloid is not the curve required. He is 

 aware that his suspension cannot be executed with such accu- 

 racy as to render the vibrations perfectly isochronal ; but he 

 may undoubtedly obtain a near approximation to a curve which 

 would render them so. — (Boston Journ. of Philosophy and the 

 Arts, May, 1824.) 



10. Method of cleaning Gold Trinkets, and of preserving engraved 



Copper-plates. 



The method used by artists for cleaning gold trinkets is the 

 application of a mixture of neutral salt, intended to disengage 

 nitric acid, with the assistance of heat. Dr. Mac Culloch re- 

 commends instead to boil the trinkets in water of ammonia, 



