Rev. H. Moseley on a Machine for Calculating Numbers. 171 



rise to crystallization, like those of frost and of congealed 

 water. Although we have rarely seen it in a liquid state, yet 

 during summer, under the influence of the sun's rays, its cry- 

 stals become perfectly liquid and assume a globular form, and 

 which they retain as they again solidify; Ibrming, in these 

 cases, conditions corresponding to water in a liquid state, ice 

 and sleet. 



XXX. On a Machine for Calculating the Products, Quotients, 



Logarithms, and Powers of Numbers. By the Rev. Henry 



Moseley, M.A., F.R.S., one of Her Majesty's Inspectors 



of Schools, and lately Professor of Natural Philosophy and 



Astronomy in Kin^s College, Lo7idon^. 

 [With a Plate.] 

 T HAVE proposed to myself in the construction of this 

 -*- machine, to determine mechanically the products, quo- 

 tients, logarithms, squares, square roots, and other powers 

 and roots of the natural numbers, by means of combinations of 

 greater simplicity than have hitherto been applied to the pur- 

 poses of mechanical calculation. 



The accompanying Plate II. is intended to illustrate theprin- 

 ciple of the machine, but it does not show the mechanical 

 details of its construction or the due proportion of its parts. 



It will be observed that it consists principally of a cone and 

 a screw. The application of the cone and the disc to various 

 purposes of mechanical calculation has long been well known, 

 and particularly by the ingenious applications made of the disc 

 to dynamical admeasurement by MM. Poncelet and Morin. 



The novelty of this instrument consists in the combination 

 of the screw with the cone. 



CD represents a small screw terminated by solid cylindrical 

 axes or gudgeons, of which that shown by the letter D is pro- 

 longed, and carries an index T. The screw admits of being 

 fixed in its bearings or made to revolve in them. 



PQ is a wheel having a hollow cylindrical axis, into which 

 is accurately fitted a hollow cylindrical piece, whose internal 

 surface is traversed by the thread of a female screw working 

 upon the male screw CD. 



The hollow axis of the wheel PQ admits of being fixed 

 upon the cylindrical piece inserted in it, or of being disengaged 

 from that piece, so that the wheel PQ may be made to°ca"ry 

 the female screw round with it in its revolutions, or to turn 

 freely upon the outside of the cylinder which contains that 

 screw, as upon an axis. 



• Communicated by the Author. 



N2 



