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A LETTER to //&f AU T H O R of the preceding PAPER, 

 with REMARKS and HINTS for the FURTHER 

 IMPROVEMENT of BAROMETERS. 

 By H. HAMILTON, B. D. Dean of Armagh, F.R.Sl 

 and M. R. I. A. 



Dear Sir, 



1 HAVE read the account you fent me of your portable Read Dec. i, 

 barometer, and as you defire my opinion of that inftrument '^^^' 

 I Ihall give it very freely. The form and ftru<5ture of your 

 barometer is as fimple and convenient as can be. The ivory 

 box is fo clofed by a cork, through which the tube pafTes, that 

 the mercury cannot get out, however the inftrument is placed 

 or agitated. Biit it feems to me that the clofenefs of the cork, 

 which is fufficient to prevent the mercury from efcaping, will 

 alfo prevent the free communicatioa that ought to be between 



the 



