103 Improvement of the Barometer. 



barometer could not indicate the current of air," for said he, "the 

 ship will have moved beyond the influence of the vyind, which was in- 

 dicated when the barometrical observation was taken." The remark 

 is worthy of consideration, and the want of a due attention to it, is 

 probably one of the causes which has aided to retard the more gen- 

 eral use of this instrument among mariners. But by far the greatest 

 cause which has prevented the universal use of the barometer, is the 

 difficulty of procuring a good one, and the still greater difficulty of 

 retaining it in perfect condition. It is not always easy to procure a 

 workman competent to construct one, and when such a man is found, 

 he is not able to devote that attention which is necessary to its adjust- 

 ment and to the boiling of the mercury in the tube, lest he should not 

 meet the views of his customers, who are in the habit of purchasing 

 at too low a price. 



We may measure mountains by observed angles, but those who 

 have tried the various methods, give a decided preference to the ba- 

 rometer, which, in some cases, is the only instrument by which we can 

 ascertain their altitude. For, the cyanometer never can be used with 

 accuracy, while sight differs with different men, or while coloring the 

 matters for the blue tints, differ so much in consequence of the soil or 

 matter which produce them, and are so subject to change by exposure 

 to the various climates. In the account of his travels and philosophic 

 researches, Baron Humboldt has, in many instances, given us the de- 

 grees exhibited by the cyanometer, but for any satisfaction to the 

 world or benefit to science, he may as well have spared himself that 

 trouble. For allowing all men to see alike — who, on being told that 

 the cyanometer exhibited 10 or 60, has any conception of the height ? 

 — We have nothing to which we can refer for accurate comparison, 

 either impressions on the brain or unalterable blue colors portrayed 

 in cyanometrical form. 



Being at Paris in July 1828, I applied to some of the most re- 

 putable philosophical instrument makers for a cyanometer, but not 

 one of them had any knowledge of it, or even knew there was such an 

 instrument. I then called on Messrs. Gay Lussac, Cuvier and Biot, 

 for information respecting it. The last named gentleman was ab- 

 sent from the capitol, which deprived me of the pleasure and infor- 

 mation I should have derived from a conversation with him. Mr. 

 Gay Lussac told me, " that he considered the instrument of very 

 little utility, and that it was found only in the works of Mr. Saussure, 

 a young gentleman of extensive scientific acquirements, who with an 



