Defoription of a Barometer. 65 
in their order, they will form a thermometrical chart, by 
which the variations of heat and cold, during the year, may 
all be feen and compared by one glance of the eye. 
By infpe@ing fig. 2. the effe& of the inftrument may be 
feen. It appears that the paper had been put on the cylin- 
der the firft day of the month, at mid-day, when the ther- 
mometer ftood at 45°; that it fell gradually till mid-night to 
25°; thereafter it rofe till the ad, at 1 P. M. when it ftood at 
42°; then it defcended at mid-night to 35°; that on the 
4th at noon it rofe to 50; and at noon the roth of the 
month it ftands at 40°. 
If 3 inches be added to the length of the cylinder, it may 
be made to delineate the variations of the barometer as well 
as the thermometer, and thereby to form a complete chart 
or view of the progrefs of both of them. And if inftruments 
of this kind were kept in different parts of the country, and 
their charts compared together, it would afford much in- 
formation with regard to meteorology, ; 
XI. Defcription of a Barometer, which marks the Rife and Pall 
of the Mercury from two different Times of Obfervation; in- 
vented by Arex. Keitu, Efg. F.R.S. and F. AS. 
Edin. From the Tranfa&tions of the Royal Society of 
Edinburgh, Vol. IV. 1798. 
As CD, fig. 3. (Plate I.) is a glafs tube bent in the man- 
ner reprefented, open at D, and hermetically fealed at A. 
From A to B is 8 inches long, and about 3 of an inch ca- 
libre. From B to C 31! inches long, and about 4 inch 
calibre. And from C to D 4% inches long, and } inch ca- 
libre. The tube is filled with mercury, the length from A 
Om E being 29 inches. When the tube is hung perpendi- 
eularly, the mercury will fall from B towards E, leaving a 
vacuum from A toB, When the atmofphere becomes hea- 
Vou. Il, E vier, 
