BOOKS.

JENYNS'S OBSERVATIONS IN METEOROLOGY.* THE results of meteorological observations reduced to tabular forms are not only dry, but scarcely intelligible save to the techni- cally skilful. This dryness does not arise from any want of at- traction in the subject itself ; but from the ignorance of the reader, and the very condensed form of expression, whioh sug- gests little or nothing to the mind untrained in meteorology. The phenomena of " the skiey influences " have not the interest of a story or a narrative, but they possess an interest of their own ; especially when conjoined with the appearances of nature, which, like the skilful background of a picture, may be made to relieve and vary the prominent object of the piece. The more striking natural phenomena, as storms of wind, thunder, rain, or snow, with the devastation they produce, the influence of either mode- rate or extreme weather upon vegetation or wild creatures—nay, the effects of meteorology on the landscape—have an attraction for the mind, whatever the source of that attraction may be.

The " Observations" of the Reverend Leonard Jenyns take a middle way. They are not a dry collection of arithmetical or technical results ; neither is science sacrificed to mere popular writing. The volume is full of facts relating to meteorology of a curious and often of an instructive kind, owing to the steady par!,, pose which pervades the book. To foresee the weather may in. deed be unattainable from the complicated conditions connected therewith ; but it seems probable that extensive observations car- ried ont in some such method as that of Mr. Jenyns might lead "to something like prophetic strain" as to the general course of the seasons. Truths, and of a larger kind than the probable weather of particular seasons, may, however, be deduced from sufficiently numerous facts ; as the permanent mean temperature of a climate, the modifying influences that may be brought to bear upon it by cultivation and in other ways. On the other hand sim- ple experiments by means of instruments may be turned to prac- tical account. Thus the minimum temperature for the ensuing night may be inferred by "ascertaining the dew-point the pre- ceding evening," and, continues Mr. Jenyns, " I need scarcely mention the importance, to gardeners especially, of being thus able to determine beforehand how cold the night is likely to be, or allude to the many instances in which, by taking timely pre- cautions against frost, they might save their more tender fruits and vegetables from being killed." Again, the proper season to plant is a moot point ; some preferring autumn, others the spring. The general laws of meteorology decide in favour of au- tumn, for these reasons.

" While the dry state of the air in spring thus favours the operations of husbandry, it leads us to see the impropriety of choosing that season for planting, which, though sometimes deferred till after winter, should be al- ways done in autumn, when the humidity is in excess. It is scarcely leas important, after shrubs and trees have been transplanted, that they should have a humid atmosphere about their branches than a humid soil about their roots. Now both these advantages are secured to them when moved towards the end of the year ; while there is then sufficient time to allow of their getting well-rooted before being exposed to the dry cutting winds of March and April. And this will further appear, when we take into account the intensity of the sun's rays in spring, owing to the very circumstance of there being so little opaque vapour to intercept them in their passage to the earth. Daniell has noticed an extremely dry state of the air, which some- times prevails for a few hours of the day in the months of April, May, and June, especially under South walls, which become very much heated from the above cause, while the dew-point is yet comparatively very low. He mentions having seen in the month of May the thermometer in the sun at 1010, while the dew-point was only 34°. It may be imagined what must be the parching effect of such an extreme state of dryness on vegetation in general, and how prejudicial it must be in particular to the tender shoots of fresh transplanted shrubs, which have not sufficient vigour to resist its influence."

The bulk of the observations were made by the author himself during a nineteen years' residence at his parish of Swaffham Bulbeck in Cambridgeshire ; but facts remarked in other places are added, and the observations of other meteorologists are used for the purpose of contrast or comparison. The names of the instruments indicate pretty clearly the nature of the more scien- tific observations : the thermometer for temperature ; the barometer for atmospheric pressure and winds—or more exactly, perhaps, currents of air, and the hygrometer for the aqueous phenomena of the atmosphere. Each instrument is made to illustrate the other when requisite ; while " sensible " observations, descriptions of nature in particular aspects, and generalized accounts as the character of the weather throughout the year enforce in a popular manner the exact facts recorded by instruments. On the various facts thus brought together Mr. Jenyns bases his " general ob- servations on the weather" and his remarks on weather prognos- tications. A chapter on thunder-storms treats the question generally. Observations on climate, and an account of that of Cambridgeshire in particular, done in the form of a monthly calendar, and somewhat after the manner of White's " Selborne," close the work.

Nothing is more uncertain than the weather, unless it be the proverbial uncertainty of life. Yet some actuaries tell us that nothing is really more regular than the average duration of life under similar conditions. In like manner the observations of Mr. Jenyns seem to show that what may be loosely called weather has a mean permanence, despite its extraordinary osoillations • Observations in-Meteorology : relating to 7bneperatere„the Mak, Atmospheric Pressure, the Aqueous Phenomena of the Atmosphere, Weather Changes, 4-e. By the Reverend Leonard Jenyns, M.A., F.L.S., &c., late Vicar of Swaffliam But- beck. Published by Van Voorst. within a certain range. Climate, both general and local, re- mains the same upon the average, though subject to alteration from geological changes, and even the action of man, as by draining and other arts of cultivation. The mean tempera- ture of any place Mr. Jenyns thinks very permanent—" how- ever this [temperature] may differ from that of other places even on the same parallel of latitude, it is remarkable how little it varies at the same place when the mean temperatures of long terms of years are compared with each other." Still there may be some doubt as to this permanence of mean temperature, when extensive changes have been made on the earth which influ- ence the air, for the permanence of temperature is merely the permanence of the conditions which cause it.

Amid all the oscillations of heat and cold, wet and dry—some- times extreme to an extent that would scarcely be expected, it is curious to notice the ranges within which they are shut up, and to trace the system of checks, balances, and compensations. The mean diurnal range of the months for nineteen years at Swaffham Bulbeck singularly counterpoise one another. Mean diurnal range January 8'.1 December 8".4

13 31. February 10'.3 November 10°.6 73 77 March 13'.2 October 12°.3 )7 13 April 15°.8 September 15°.7 37 77 May 18'.6 August 15°.3 33 3) June 17'.1 July 17°.6 May, on the confines of spring and summer, exhibits the greatest range of the whole year, and the greatest discrepancy between its corresponding month, though even that is little more than three degrees. The diurnal range in summer is nearly double that of winter, being for summer 17°.2 and only 9° for winter.

Mean temperature is, however, a very misguiding thing as to sensations or health, and quite consistent with most enormous ranges. Here are some curious facts as to winter and summer -almost changing places.

"It is a curious circumstance, and a striking proof of the extreme uncer- tainty of an English climate, that, during seasons of an unusual character, we sometimes have the same temperatures occurring for one or more days at the two opposite periods of winter and summer. I have known the thermome- ter on Christmas-day higher than it had been on the Midsummer-day preced- ing. On the two last days in June 1839, the temperature never rose higher than 54' (on the 29th) and 53' (on the 30th), while on the 23d of December following it got up to 551°. On three consecutive days in June 1841, (the 7th, 8th and 9th,) the maximum temperature did not exceed 52', 54°, and 5,5' respectively, while on each of the two last days in December 1842 it was also 55'. On the 25th of June 1835, the maximum temperature was actually as low as mr, while in December 1848, for seven days in succession, it was never lower than 53°, several times as high as 55', and on one occasion (the 8th) as high as 58'. This last was the highest temperature I ever registered in the month of December. During most of these very mild days the weather was extremely fine, the thrush was heard in full song, peacock but- terflies were on wing, and, as far as the appearances of nature went, it was difficult to persuade oneself it was not spring instead of winter."

The same reversal as it were of the natural order of things may prevail in every month of the year, though not, we imagine, at the same time.

"January, though usually the coldest month, may be milder than either February, March, or April. It is also remarkable that a higher mean has been attained in January than in February. "February may be milder than either March or April.

" March may be warmer than April, but never attains the temperature of May

" April may be warmer than May, but never attains the temperature of dune. On the other hand, it is observable that the lowest mean temperature of April is exceeded by the highest mean of all the other months of the year ; so we might suppose it possible that in certain years it might be the coldest month of any, though in fact this probably never occurs.

"In like manner the highest mean of May exceeds the lowest mean of June, July, and August, though a year seldom occurs in which it is really the hottest month. It is a singular circumstance, and a striking instance of the strange irregularity of an English climate, that two months should be thus next each other, one of which sometimes has the same temperature as that which is ordinarily the coldest month in the year, and the other some- times the same temperature as that which is ordinarily the hottest.

"June, July, and August, generally the three hottest mouths, may, any one of them, be colder than September. "September may be colder than October, but October is never colder than November.

"November may be 6' colder than December, and December to a still greater extent (nearly 131 degrees) colder than January."

The mere observation of the senses is of course worth very little ; for not only do men feel differently according to their habits and constitution, but the same man feels differently according to his health, or his being. full fed, or the temperature he has just quitted. Experience is not worth much, for independently of pre- judice, and the uncertainty of temperament or condition just alluded to, it does not make its observations with the regularity and system of the scientific observer, and is probably in bed when it should be abroad. Every one has heard of snow in harvest ; in the extreme North we believe it is a not uncommon fact. The oc- currence of frost in the summer months would hardly be looked for; yet it takes place except in July, and most probably then. "It is also an important fact that there is scarcely a month in the year in this country in which frosts arising from terrestrial radiation are not liable to occur. I have known frosts in June at Swaffham Bulbeck in two or three instances. On the 29th of that month, in 1837, at sunrise, and for a short, time afterwards, the ground was white in places with hoar frost. Again, on the 13th of June, in 1849, (the instance above alluded to,) the radiating thermometer fell 2i degrees below freezing-point. • * * * I have likewise known a frost in August. There was one on the 22d of that month in 1850, at Ampney in Gloucestershire, where I was staying at the time. I had no thermometer with me to indicate the exact degree of cold that took place, but the ground was still white with frost when I rose at six in the morning, and in the garden there were unmistakeable marks of its effects upon some of the more tender plants and vegetables. Even in July, which at least might be supposed an excepted month, the radiating ther- mometer once fell at Swaffham Bulbeck to 32e. This was in 1849,

the same year as that in which a frost had occurred in June ; and though the temperature in that instance was not quite down to freezing-point, it was so near it, that it is difficult to believe it might not sometimes be slightly further depressed, so as to reach 32' itself, if it did not go below it Of course, in all the other months of the year frosts are of frequent occur- rence."

These kind of topics might be pursued further as regards tem- perature, and we could enter into all the other questions discussed by Mr. Jenyns. Enough, however, has been done to indicate the nature of the book, which those interested in the subject may con- sult to their advantage.