112 



BAROMETEK. 



BAROMETER. Some points relative to uses 

 of the barometer, especially for the measure- 

 ment of heights and the foretelling of weather 

 changes, will be found considered in the volume 

 of this CTCLOP-EDIA for 1862, under the titles 

 BABOMETER and METEOEOLOGY. The present 

 notice will be confined chiefly to an account of 

 certain results, practical and theoretical, ob- 

 tained by use of the instrument, and also of 

 certain recently constructed forms of it, in par- 

 ticular those of the self-registering class. The 

 reader is referred also to the article ATMOS- 

 PHERE, in this volume. 



It may here be briefly mentioned that, a 

 paper having appeared in the 28th volume of 

 the Philosophical Magazine (1864), from the 

 pen of Mr. Charles Packe, asserting a discrepancy 

 between the barometric pressures correspond- 

 ing to the French and the English boiling- 

 points, and attributing the larger part of this 

 to a supposed difference in the scales them- 

 selves, arising through the difference of the 

 standard temperatures Centigrade, and 62 

 Fahrenheit of the units of length adopted by 

 the two nations, Mr. William Mathews replies, 

 dissenting from those views, and, while admit- 

 ting that the metrical scale is not always prop- 

 erly graduated, claims that where it is so, the 

 readings of the French barometer-scale, if re- 

 duced by Guyot's Tables in which millimetres 

 at C. are directly expressed in parts of the 

 inch at 62 F., must coincide exactly with 

 those of the scale usual wherever the English 

 inch is taken as the unit. Mr. J. E. Blackwell, 

 England, patented, about the beginning of 1864, 

 an improved aneroid barometer, the peculiar 

 feature of which is that each instrument in- 

 cludes four or more chambers, instead of a 

 single one as in the earlier forms ; the connec- 

 tion of the springs within these chambers with 

 tho index is such that inaccuracies of action in 

 any one of the chambers is compensated by the 

 action ol*the others. 



Correction for Temperature, in the Measure- 

 ment of Heights. In the journal above quoted, 

 for August, 1865 (vol. xxx.), appears a paper 

 which was read before the Royal Society in 

 May of the same year, by Mr. Alexander J. 

 Ellis, entitled, " On the corrections for Latitude 

 and Temperature in Bai'omctric Hypsometry, 

 with an improved form of Laplace's formula," 

 and in which the subjects named are very mi- 

 nutely and fully discussed. 



In the part of this paper devoted to the sub- 

 ject of temperature, occurs the most concise 

 expression the writer of this notice has met 

 with, of the results in the given respect of Mr. 

 Glaisher's observations. Tnese, it is stated, in- 

 dicate that, under a clear or nearly clear sky, 

 there is a fall of about 5 F. for each of tho first 

 4 inches of depression of the barometer ; then 

 of about 4.2 per inch, from the 5th to the 13th 

 inch; and about 4.5 from the 14th to the 16th 

 inch ; while, under a cloudy sky, we may 

 expect on an average a fall of very nearly 4 F. 

 for each inch of depression of the barometer 



the 1st inch, however, and the llth to the 16th, 

 being accompanied with a slightly more rapid 

 fall of temperature. Such may therefore be re- 

 garded as, in the given latitude and climate at 

 least, and under the circumstances named, the 

 normal alteration of temperature with height. 



In view especially of the different rates of 

 variation (with increasing height) of the ba- 

 rometer and thermometer, or, in other words, 

 of the deviations of the temperatures from a 

 strictly uniform law, the conclusion is arrived 

 at that, in determining altitudes by the barom- 

 eter, it is best to proceed by several partial 

 heights, each not exceeding 3,000 feet, and also 

 to take fresh observations whenever the tem- 

 perature has been found to alter abnormally. 

 Mr. Ellis urges that there should be two ascend- 

 ing parties, one for each variable station, and 

 each of which should be able to signal to the 

 other ; while a stationary observer at the low- 

 est station would serve as a check on the other 

 two. 



Barometric Observations in the Arctic Re- 

 gions. The 13th volume (1863) of the Smith- 

 sonian Contributions to Knowledge contains a 

 paper of great length, entitled, "Meteorological 

 Observations in the Arctic Seas," &c., these 

 having been made by Sir F. L. McClintock, on 

 board the yacht "Fox," in Baffin Bay and 

 Prince Regent's Inlet, 1857-'58-'59 ; and their 

 reduction and discussion having been accom- 

 plished at the expense of the Smithsonian In- 

 stitution, by Mr. Charles A. Schott. The paper 

 is in three parts, the first treating of tempera- 

 tures, and the second of the phenomena of arctic 

 winds and storms, including the barometrical 

 curves for certain storms. 



In the third part, are presented tables of 

 4-hourly readings of the aneroid barometer, those 

 used in the discussion of the subject, extending 

 from September 1st, 1857, to August 31st, 1859, 

 and corresponding to latitudes varying from 

 60 to 75.3, K, and longitudes of from 53.7 

 to 94.4, W. ; and also of the marine mercurial 

 barometer, September 20, 1857, to April 16, 

 1858, corresponding to latitudes of from 69.4 

 to 75.2, K, and longitudes of from 59.l to 

 69. 1, W. No separate record was kept of the 

 aqueous vapor pressure, so that this could not 

 be eliminated ; but its amount being small, this 

 is of less importance. 



The results obtained by reduction of these 

 two series of tables afford the means of com- 

 paring the two barometers, and of deducing a 

 correction for tho indications of the aneroid, in 

 order to make these correspond with the read- 

 ings of the mercurial, referred to 32 F. of tem- 

 perature. Thus, a comparison of the mean 

 readings of the two barometers, for the months 

 of September, 1857, to April, 1858, inclusive, 

 shows throughout a very nearly constant differ- 

 ence. The mean of the several monthly differ- 

 ences for the period indicated is .221 of an inch 

 of mercury the aneroid barometer reading 

 being by so much too high ; so that the correc- 

 tion required in the aneroid readings may bo 



