72 • PHILOSOPHICAL TRANSACTIONS. [aNNO 1666» 



then so much money be paid him by the other party as the said invention was 

 valued at. 



A new Covtrwance of a Wheel-Barometer. By Dr. Hook. 



N° 13, p.2lS. 



This is only an easy way of applying an index to any common baroscope, 

 whether the glass be only a single tube, or have a round bolthead at the top. 

 And by it the variation in the altitude of the mercurial cylinder, which at most 

 is hardly three inches, may be made as distinguishable as if it were three feet, 

 or three yards. 



The manner is evident by figure 5, pi. 1, where ABC represent the tube, 

 which may be either blunt or with a head, as A. This is to be filled with 

 quicksilver, and inverted as usual into a vessel of stagnant mercury of the 

 shape I K, that is, having its sides about three or four inches high, and the 

 tube equally wide both above and below ; and, if possible, of equal capacity 

 with the hollow of the tube about B : for then the quicksilver rising as much 

 in the hollow of I, as it descends at B, the difference of the height in the 

 receiver I, will be just half the usual difference. And if the receiving vessel 

 I K have a larger cavity, the difference will be less ; but if less, the difference 

 will be greater : but whether the difference be made more or less, it is no 

 great matter, since by the contrivance of the wheel and indexj 4fhe least varia- 

 tion may be made as sensible as is desired, by diminishing the width of the 

 cylinder E, and lengthening the index F G, according to the proportion 

 required. 



Of four Sims and tivo uncommon Rainhoivs observed in France. 



N" 13, p. 219. 



On the gth of April 1 QQQ, about half an hour past Q, there appeared three 

 circles in the sky. One of them, SCHN, fig. 6, pi. 1, was very large, a 

 little interrupted, and white every where, without the mixture of any other 

 colour. It passed through the middle of the sun's disk, and was parallel to 

 the horizon. Its diameter was above 100 degrees, and its centre not far from 

 the zenith A. 



The second D E B O, was much less, and deficient in some places, having 

 the colours of a rainbow, especially in that part which was within the great 

 circle. It had the true sun for its centre. 



The third H D N, was less than the first, but greater than the second ; it 

 was not entire, but only an arch or portion of a circle, whose centre was far 



