154 



Barometric Observations. 



The place of observation is situated in the township of Crump- 

 sall, about two miles N. by E. from Manchester. The barome- 

 ter is a common upright one, and the internal diameter of the 

 tube bears so small a proportion to that of the bulb, that the 

 connection is too inconsiderable to merit any attention, being 

 only "277^77 P^''' of the whole scale : that is, the scale of four inches 

 should be diminished by 3^^^ of an inch. The surface of the mer- 

 cury in the bulb is ISj feet from the ground, and about 248 feet 

 above the level of the river Irwell where it flows under the bridge 

 at the bottom of Bridge Street, Manchester ; to which place it 

 is navigated by the flats of the Mersey and Irwell Navijoation 

 Company. A mean of four attempts to determine the elevation 

 of the surface of the mercury in the bulb above the bridge baro- 

 metrically, gives 220 feet ; and the height of the bridge above the 

 level of the river measures exactly 28 feet. If, therefore, the 

 elevation of the barometer above the level of the sea (which I 

 have reason to believe may be somewhere about 320 feet) were 

 carefully ascertained, the elevation of the bridge, and of the river 

 below it also above the same level, would be easily determined. 



I am &:c. 

 To Mr. Tilloch, John Blackwall. 



Hafod, Mold, Flintshire, Feb. 13, 1821. 



SiK, — I beg leave to transmit to you my observations made 

 yesterday with a barometer of Sir H. Englefield's construction 

 made by T. .Jones. The situation I take to be about 500 feet 

 above sta level, but the altitude has not yet been accurately taken. 

 It is 16 miles South West of Liverpool. I am &c. 



To Mr. Tilloch. Wm. Ward. 



Sir, — I should feel much gratified could any of your readers 

 furnish such information as would reconcile the following levels, 

 (which are apparent contradictions of each other) as it would 

 give the fall of the Thames from Brentford to Limehouse, and 

 be a great assistance in forming an estimate of the height of 

 London above the sea. 



The 



