12 



Fabrication 

 and price of 

 tiiese barome- 

 ters. 



PORTABLE BAROMETER- 



circumstances, barometical observations will give a much more 

 accurate idea of the outline of a countiy than any we now pos- 

 sess ; and it should be ever remembered, that observations ac- 

 curately made, and faithfully recorded, are valuable. The 

 repeated observations of different travellers, though separately 

 defective, will in most cases correct each other, and from' the 

 whole very accurate conclusions may be drawn. 



I have entered into a greater detail than would be necessary 

 for a great part of your readers, in the hope of being intelligi- 

 ble to those who are less acquainted with the subject, and who 

 may wish to employ any instrument-maker for the construc- 

 tion of barometers similar to that which I have described. In 

 justice to a very ingenious young artist, permit me to add, that 

 I have employed in making those which I have, Mr. Thomas 

 Jones, of No. 120, Mount-street, Berkeley -spuare, pupil of 

 the late Mr. Ramsden, and who will furnish them at the price 

 of two guineas and a half without the attached thermometer, 

 three guineas with it, and three guineas and a half with the 

 attached and detached thermometer. Such barometers, how- 

 ever, as are graduated down to 20 inches, will, on account of 

 the additional work, cost five shillings more. 



Tilney -street^ 

 April 5, 1806. 



am, Sir, 

 Your humble Servant, 



H. C. Ekglefield, 



Difference of P. S. On comparing several barometers made by Mr. 



settlinc of these J*^"^^* since this description was written, I find that in some 



instruments: It of them the mercury does not take its true height on turning 



their accuracy. "P ^^^^ instrument, quite so quick as in the two which he first 



constructed for me. This difference is owing to the greater 



closeness of fibre in some pieces of box-wood than in others ; 



but it does not affect the accuracy of the instrument. It may 



not be superfluous to say, that the weight of this barometer is 



one pound and three quarters ; the weight of Ramsden's last 



improved barometer is four pounds and a half ; and that of 



his earliest form, six pounds and three quarters. 



1 subjoin a few observations made at the top and bottom 

 of Richmond-Hill, by which the accuracy of this barometer 

 may be fairly estimated. 



Dec. . 



