ARTICLE X.

On the Height of the Barometer. By M. P. Moyle, Esq.

(To the Editor of the Annals of Philosophy.)

DEAR SIR,

Helston, April 15, 1823.

A PROPER Collection of accurate barometrical observations would give us a correct idea of the height of the different places where they are kept above the level of the sea, as well as serving other useful purposes; but unless every necessary correction is made, this cannot be obtained. From the few observations that I have made on those tables which have appeared in the Annals, this consideration does not seem to have been properly meditated. It may not, therefore, be unacceptable to such of your correspondents to make a few remarks on this particular point, and thereby prove its necessity.

It is well known that mercury expands by heat, and contracts on the application of cold. Hence the height of the mercurial column in the barometer is affected not only by the pressure of the atmosphere, but by the temperature, and the attention of meteorologists ought to be more fully drawn to this consideration to render their tables of the greatest utility.

The standard temperature for observation is agreed on all hands to be 32° of Fahr.; consequently if made at a time when the thermometer stands above or below this point, it must of necessity indicate a higher or lower range respectively; and to prove the extent of error arising from the neglect of this circumstance, let us suppose that the height of 30 inches of mercury is taken when the attached thermometer stands at 72°; this would give an excess above what it would be at 32° of more than ths of an inch from the mere expansion of the mercury. No wonder then that errors arise in our calculations.

100

General Roy found that the expansion of one inch of mercury in the barometer tube at 32° was 0001127: hence to reduce the observed height of the mercury to what it would be at 32°, becomes an easy matter; but for the greater facility, I have constructed the following table, which represents the expansion of one inch of mercury for its corresponding temperature. It extends from 32° to 150° beyond which it is not probable that any observation will be made.

In order to obtain the exact temperature of the mercury, the observation should be made by a thermometer attached to the frame of the barometer, that it may warm and cool along with it.

There are different ways to calculate the correction from this table; the first, and most accurate, is, that of multiplying the sum in the table corresponding with the observed temperature by 30, which gives the expansion for 30 inches of mercury. Then let the observed height of barometer be 28-420, attached thermometer 72°, and we shall have 4348 x 30 = 13044. Then 30-13044: 30:: 28-420 = 28-29697.

The second, the one I always adopt, as being more expedi tious, is by multiplying the sum corresponding with the temper ature by the observed height of mercury, and then taking it from the observed height, viz. 4348 x 28-42 = 1.2357 - 28-420 = 28-29643, differing a mere nothing from the first method.*

It appears from the Ann. de Chim. et Phys. that the meteorological table published monthly in them has the proper correc

The correction obtained by this method must be added to or subtracted from the observed heights, according as the temperature is below or above the standard temperature, or 32° of Fahr.

tion made, and that it is marked at nine in the morning, at noon, at three in the afternoon, and at nine at night.

From the monthly mean of these heights, it appears that the barometer is highest at nine in the morning, next highest at nine in the evening, lower at noon, and lowest of all at three in the afternoon. The proper hours, therefore, for taking the heights of the barometer is nine in the morning, and at three in the afternoon.

The elevation of the barometer above the level of the sea ought also to be noted when known; and if a correction is made for it in the results given, it should also be remarked, as some meteorologists allow for it, while others are guilty of the I am, dear Sir, your humble servant,

omission.

M. P. MOYLE.

ARTICLE XI.

Some Particulars regarding the Ashmolean Catalogue of Extraneous Fossils, published in Latin by Mr. Edward Luid (or Llwyd); and recommending a Translation of the same to be made and printed. By Mr. John Farey.

SIR,

(To the Editor of the Annals of Philosophy.)

Howland-street, March 29, 1823.

In pursuance of a design which I formed some years ago, of collecting as many as possible of the published localities of fossil shells, and of other organic remains, in some instances, I lately made an alphabetical arrangement of the 294 places, to which Mr. Edward Luid (or Llwyd) seems to me to refer, in the second edition of his descriptive Catalogue of the Ashmolean Museum at Oxford, printed in 1760. This book I borrowed of my friends Messrs. Sowerby, having, after many years inquiry, never been able to meet with a copy of it on sale, from whence I conclude that it is out of print, and become very scarce and dear; which circumstances induce me to request you to give insertion in the Annals to a few particulars regarding Mr. Luid's work, with the hope that the same may excite the attention of the collectors of fossil shells, &c. and prove of some use to them, and may lead to the publishing of an English edition of this work, by some gentleman connected with the University; wherein I hope, that the copper plates to Mr. L.'s book are preserved, and might serve for a cheap English edition.

The specimens of organic remains, &c. mentioned, and briefly described, by Mr. Luid, including some sparry substances at the beginning, seem about 1800 in number; 1766 of which specimens are distinguished by a series of numbers, and some others

are interpolated, and marked a, b, c, &c. in addition to the number.

The local index which I have made shows, that 30 places, which I shall mention presently, furnished more than one-half of the whole collection, or 1065 of the specimens enumerated'; consisting of 477 fossil shells, and 588 other bodies, mostly organized; the produce, apparently, of twelve of the assemblages of strata, ascertained by Mr. William Smith, and enumerated in his Geological Table, from the London clay downwards to the lias. It hence appears, that 25 of the places, among the most productive of Ashmolean speciniens, furnished none to the Smithean collection, of about 1155 specimens of shells, &c. which Mr. S. in June, 1816, deposited in the British Museum,* whose localities, he has partly mentioned in two quarto works, "Strata Identified," and a "Stratigraphical System" (but which works, unfortunately, remain unfinished); and which localities, as far as they have been published, are enumerated in alphabetical order, in the "Philosophical Magazine," vol. 50, p. 271.

For the purpose of ascertaining the strata of the following places, I have consulted Mr. Smith's separate "Geological County Maps," except as to Lincoln and Northampton counties, which are not yet published, and as to which, I have consulted his original "Geological Map of England," published in September, 1815; which last was accompanied by an interesting "Memoir," which has, I think, been strangely overlooked, by almost every subsequent writer.

1. From the London clay, on the N shore of Sheppy Island, near Minster, in Kent, 5 shells and, in all, 25 specimens, are described by Mr. Luid.

2. From the Portland rock, at Brill, 10 miles W of Aylesbury, Bucks, 11 shells and 2 other specimens.

3. From the Coral rag and pisolite, at 6 places; which, beginning south-westward in the range of these strata are as follows, viz. Faringdon, 13 miles W of Abingdon, Berks, 29 shells and 89 others; these 118 specimens being the greatest number from any one place; Garford (or Garvord) 4 miles W by S of Abingdon, Berks, 9 shells and 26 others; Marcham, 2 miles W by S of Abingdon, Berks, 40 shells and 54 others; Bessel's-Leigh (or Basie's L.) 3 miles NW of Abingdon, Berks, 16 shells and 10 others; Chawley, 4 miles N by W of Abingdon, Berks, 5 shells and 13 others; and Stanton (St. John's) 3 miles NE of Oxford, 5 shells and 11 other specimens.

4. From the Woburn sand, at 3 places, viz. Cumner, 44 miles N by W of Abingdon, Berks, 6 shells and 10 others; Bullington, 14 mile SE of Oxford, 28 shells and 28 others; and Stafford Grove, 24 miles ENE of Oxford, 2 shells and 11 other specimens.

* See vol. xi. p. 364 of the First Series of the Annals, also the Phil. Mag. vol. li. p. 180. The places common to both collections are, Kelloways B.; Marsham; Sheppy I.; Stonesfield; and Towcester.

5. From the Clunch clay, at 2 places, viz, Oxford city, Sunk Fences or Walks, &c. 19 shells and 7 others; and Cowley, mile SSE of Oxford, 41 shells and 27 other specimens.

6. From Kelloway's stone, at Kelloway's Bridge (or Calloway B.), 2 miles NE of Chippenham, Wilts, 13 shells.

From the Cornbrash, at 5 places, viz. Witney, 4 miles NNE of Bampton, Oxfordshire, 46 shells and 63 others; Kidlington, 24 miles SE of Woodstock, Oxfordshire, 21 shells and 13 others; Islip, 4 miles SE of Woodstock, Oxfordshire, 13 shells and 13 others; Charlton, 3 miles S of Bicester, Oxfordshire, 5 shells and 24 others; and Raunds (or Rance), 34 miles S of Thrapston, Northamptonshire, 10 shells and 10 other specimens.

8. From the Forest Marble at Stonesfield (or Stunsfield), 24 miles W of Woodstock, Oxfordshire, 6 shells and 51 other spe cimens.

9. From the Upper Oolite, at 3 places, viz. Towcester (or Tocester), 8 miles SSW of Northampton, 9 shells and 6 others; Wellingborough, 61 miles S of Kettering, Northampton, 7 shells and 6 others; and Desborough, 4 miles NW of Kettering, Northamptonshire, 8 shells and 16 other specimens.

10. From the Fuller's-earth, at Marston Trussel (or Merston T.), 114 miles WNW of Kettering, Northamptonshire, 13 shells and 11 other specimens.

11. From the Under Oolite, at 4 places, viz, Birlip Hill, 5 miles ESE of Gloucester, 9 shells and 4 others; Barrington (Great?) 5 miles E of Northleach, Gloucestershire, 22 shells and 12 others; Upton, mile W of Burford, Oxfordshire, 7 shells and 9 others; and Byfield, 6 miles SW of Daventry, Northamptonshire, 21 shells and 3 other specimens.

12. From the Lias, at 2 places, viz. Parton Passage (or Pyrton P. on the W shore of Severn River), 4 miles SSW of Newnham, Gloucestershire, 23 shells and 28 others; and Whitton (on S shore of Humber River), 10 miles W of Barton, Lincolnshire, 28 shells and 11 other specimens are described, and part of them figured, by Mr. Luid; 56 of which latter are shells.

Five out of the above 30 places, the least production of shells, &c. have furnished Mr. L. with 13 specimens each; all the other 264 places mentioned in his work, gave less numbers than 12 specimens each to the Ashmolean collection, except, perhaps, some of those unnamed places, included under the respective county names.

In a new edition of Luid, I beg to suggest that the several specimens figured, should be pointed out by a reference to the number of the plate or table. The want of these references, and the apparently random placing of the figures in the plates, are at present very perplexing; and, lastly, I request, that an index to the several localities may accompany such edition, towards the preparing of which, I would gladly lend assistance; and am, Yours, &c. JOHN FAREY,