308 i'HILOSOPHICAL TRANSACTIONS. [aNNO 1729. 



the oily substances insinuate themselves more and more between the particles of 

 the stone; by which means, when the stone cools again, and shrinks, they 

 seem to prevent these particles from coming as close, and within their sphere 

 of activity, as the remaining particles may, where no such foreign matter has 

 been applied ; by which means they also cannot attract each other so strongly 

 as tlie rest, and must therefore remain separated. Fat and oily substances seem 

 to be most fit for this purpose, as they are endued with a repelling force. 



Of the Nature and Firlues of the Holt Waters, from the Rev. Mr. J. Lewis, 

 ricar of the Place. N° 408, p. 43. 



Experience has proved tlie Holt waters to be of admirable efficacy in scor- 

 butic and scrophulous cases. They are of an attenuating, astringent, and 

 drying nature : by which qualities they probably perform their cures. This 

 latter quality, it is probable, they derive from the alum and iron supposed to 

 impregnate them. The ingredients, which give them their drying, absorbing 

 and healing quality, are the sulphur and ochre ; by which they imbibe the pec- 

 cant humours, and sheath the sharp salts, that lance and tear the finer glands, 

 and cause blotches, and ulcerations. As they attenuate and astringe, they are 

 a noble diuretic, removing obstructions from the kidneys, and causing the renal 

 glands to make their due secretions, and at the same time dissolving the grosser 

 salts, and fitting them to be carried off through the urinary passages. 



A further Account of a new Machine, called the Marine Surveyor, contrived for 

 the Mensuration of the H'ay of a Ship at Sea, more correctly than by the Log. 

 By Mr. Henry de Saumarez, of the Island of Guernsey. N° 408, p. 45. 



In fig. 1, pi. 8, F represents the boat, through the rudder of which a small 

 spindle passes, in an iron pipe, of which hg is the length. To the point g are 

 fastened the 4 iron fins, or flyers, a, b, c, d, in a square form, the bars db and 

 AC to which they are fixed, lying in an horizontal position. These flyers are so 

 contrived, as to have full play in any motion of the boat. To the point h, 

 which is the upper part of the pipe and spindle, is fixed the dial e. Now the 

 boat being put into motion, the flyers move accordmgly, which proportionally 

 affecting the spindle, the motion is thereby communicated to the dial, which 

 may be fitted to strike the miles or leagues the vessel runs. 



But to describe the first movement of this machine more exactly, fig. 2, re- 

 presents it unfixed. The cross, or bars db and ac, lie flat, or in an horizontal 

 position; the arbor or perp. spindle, screws into the point g, and passes through 

 an iron pipe to the dial, as follows. The flyers a, b, c, u being fitted to move 



