29(5 SCIENTIFIC NEWS, 



Befides tliefe improvements on the common fleam-engine, 

 he has alfo found means to apply (he fame principles to the old 

 engine, known by the name of Savary's, in fuch a way as to 

 render the fame a powerful and ceconomical engine for a great 

 variety of purpofes. 



Such is the outline of Mr. Woolf's improvements on this 

 ufeful engine: but, for the general information of practical 

 engineers, we ftiall fubjoin a more technical ck fcription, in 

 Mr. Woolf's own words, extracted from his fpccification of 

 his patent. 



(To be continued.) 



. SCIENTIFIC NEWS. 



Geometry* 



Two theorems -O^UYGENS has given the two following theorems in his 



from the Ho- Horolo»ium Ofcillatorium, which are applicable to all folid 



rologium of o j > r r 



Huygens. bodies: " The center of of dilation, and that of fufpenfion are 



always reciprocal to one another. The fame body is always ifo- 



chronal to itfelf while it ofcillates round parallel axis's taken at 



equal diftances from the center of gravity. M. Biot has given 



a remarkable extenfion to thele two theorems. 



—extended far- All thefe parallel axis's form the furface of a right angled 



tner by M. cylinder of which the axis paiTes through the center of gravity. 



But the analytical expreflion under which M. Biot prefents 



the theorem of Huygens, made him inflantly perceive, that 



an arbitrary inclination might be given to this axis, the 



radius of the cylinder being fuitably changed at the fame 



time; and that thus according to the different degrees of 



inclination of the axis, an infinity of cylinders might be 



obtained. The fuperficies of which cylinders fliould have the 



fame property as that of the primitive cylinder. Befides this, 



the axis without changing its inclination may defcribe a 



conical furface about its primitive pofition, which will multiply 



the number of cylinders already found, as often times as 



right lines can be conceived to be drawn on the upper furface 



of the cone, 



5 Aftronomy^ 



