On the construction of the Barometer, 8fc. 293 



ment would be brought naturally to the inference, that in as much as 

 good Barometere are constantly being made somewhere, if he cannot 

 obtain one here, he can do so abroad. 



I do not suppose however that either yourself or the writer would 

 ' wish to increase the already unfavorable prepossession which to some 

 extent exists, to the prejudice of the instrument makers of this coun- 

 try. They labor it is true under disadvantages in the manufacture 

 of some pai'ts of a philosophical apparatus, which are not experienced 

 elsewhere. But the Barometer does not belong to this class. In 

 its construction nothing is wanting but a proper knowledge of the 

 principles it involves, and that facility of manipulation which expe- 

 rience usually yields. 



On visiting London and Paris in the years 1830 and '31 for the pur- 

 pose of availing myself of the great advantages which those cities afford 

 for improvement in mechanical skill, as well as the collation of phi- 

 losophical facts, and while there, being engaged in some experimental 

 observations on the construction of the Pyrometer, I had frequent 

 intercourse with one of the most deservedly distinguished instrument 

 makers of the former city, who 1 found entertained a more favorable 

 opinion of the extent of the demand for good instruments in the Uni- 

 ted States than my experience authorized ; that opinion doubtless 

 arises from the frequent orders he received to furnish such for this 

 country. It may be proper to remark that many of these were of a 

 character that could have been readily furnished here, had there ex- 

 isted that confidence which many of our own workmen ai'e entitled 

 to receive. 



Conceding however the imperfections of the ordinarily manufac- 

 tured Barometer, I cannot join with the writer in attributing to this 

 circumstance mainly the existing neglect of so useful an instrument, 

 when used as a Aveather glass ; but would rather refer it to the 

 lengthened series of observations it is necessary to make in every 

 particular place, before such satisfactory general rules can be dedu- 

 ced as will enable us to infer from specific movements in the baromet- 

 ric column definite changes of weather, few persons being found wil- 

 ling to make periodically precise observations. 



In conclusion I may be allowed to remark, that in view of the ad- 

 vancement of meteorological science, the want of uniformity both in 

 the principle and construction of the various instruments used 

 throughout this extensive country, in order to furnish correct meteo- 

 rological tables, is certainly to be regretted, and any plan that could 



