440 PHILOSOPHICAL TRANSACTIONS. [aNNO 17 IQ. 



of his barometer is very small. So that there is no need to have recourse to 

 any peculiarity, either in the quicksilver or the glass of which that tube was 

 made ; or to an unperceived remnant of air left in the tube, from some of 

 which causes that effect and some others of the same kind were imagined to 

 proceed. 



Corol. 2. — In a barometer made with a small tube, the mercury will rise and 

 fall irregularly. For, as the height of the mercury depends partly on the dia- 

 meter of that part of the tube that touches the upper surface of the mercury, 

 it is plain, that the unavoidable inequalities in the diameter of the tube will be 

 more considerable, in respect to the whole diameter ; and consequently will 

 affect the height of the mercury more in a small tube than in a wider. And 

 this I take to be the reason why it is so very difficult, not to say impossible, to 

 make two barometers which shall exactly agree in the height of the quicksilver, 

 in all constitutions of the air, especially if the tubes be very narrow. This 

 irregularity is still more considerable in the pendent barometer, in which the 

 quicksilver moves through a large space, in order to make a small alteration in 

 the length of the column suspended: the same consideration is easily extended 

 to those levels, that depend on the rising of mercury to the same height in the 

 opposite legs of a bent tube ; an instrument of which kind has been lately 

 offered for the service of the public. And as the effect is just contrary in levels 

 made with water or spirit of wine, due regard ought to be had to this property 

 in the construction of those instruments, by making the tubes sufficiently wide, 

 in order to diminish the error as much as possible. 



u4n Account of a wonderful Fall of Water from a Spout, on the Moors in Lan- 

 cashire. By Dr. Rd. Richardson. N° 363, p. IO07. 



This remarkable spout fell on Emott-moor, near Coin in Lancashire, June 3, 

 17 18, about 10 in the morning. Several persons who were digging peat near 

 the place where this accident happened, on a sudden were so terrified with an 

 unusual noise in the air, that they left their work and ran home, which was 

 about a mile from the place : but to their great surprise they were intercepted 

 by water ; for a small brook in the way was risen above 6 feet perpendicular in 

 a few minutes time, and had overflown the bridge. There was no rain at that 

 time on Emott-moor, only a mist, which is very frequent on those high moun- 

 tains in summer. There was a great darkness in the place where the water fell, 

 without either thunder or lightning. The meadows at Wicolae were so much 

 flooded, that the like had not been seen in several years before, though it was 

 there a very bright day. 



