138 KEPORT OF THE 



ARTICLE IX. 



Report of the Meteorological Committee. 



The Committee of the Maryland Academy of Science and 

 Literature, to whom was confided the charge of co-operating 

 in the Meteorological Observations, proposed to be continued 

 on four fixed periods of the year, beg leave to present the fol- 

 lowing report and tables : 



It being an object of great interest, before making, as well 

 as before describing such observations, to be provided with a 

 set of accurate and well constructed Meteorological Instru- 

 ments, the Committee applied themselves first of all, to the 

 arrangement of a barometer, more suitable to the occasion, 

 than those constructed for ordinary purposes. As the best 

 account of the instrument now in the possession of the Aca- 

 demy, and of the novel and excellent arrangement which 

 characterizes it, they would give here the description fur- 

 nished at their request by the successful artist himself: — 



'Gentlemen : — Having been directed to construct a standard 

 barometer for the use of the Meteorological Committee of the 

 Maryland Academy of Science and Literature, I submitted to 

 you a plan for such an instrument. Upon your approval of 

 the modifications I-proposed to introduce, and of the general 

 method offered for its manufacture, I executed for you an 

 instrument, of which, at your request, I furnish the following 

 description. 



The glass tube is 32.5 inches in length ; 0.25 internal, and 

 0.60 external diameter ; the upper end being hermetically 

 closed, the lower extremity was ground to a slightly conical 

 form for a length of L25 in. for the purpose of being fitted air- 

 tight within a pierced circular plate of glass through which 

 the tube passes about one inch ; the tube and plate are so 

 ground to each other, that, when the former is placed verti- 

 cally, the latter shall be perfectly horizontal. This plate, 

 which has a diameter of 3 inches, and a thickness of 0.20, 

 forms the upper part or cover of the cistern, and is introduced 

 for the purpose of furnishing a horizontal surface, against 

 which, the mercury of the cistern may extend and contract in 

 its changes of volume, arising from tiie varying length of the 



