First, respecting the effect of the moon in her various phases, he shows that, with regard to temperature, there is "a system of variations governed by her attraction, as a secondary cause, subject, of course, to the more powerful influence of the sun in his declination." The precise effects, however, on the temperature, are less clearly shown than might be wished. He observes, that the elevations of the barometer and thermometer, during the same periods, are found mostly in opposition to each other, but at times in conjunction. "In the early cold periods of the year, and in the fine weather of summer, opposition will be found predominant; but in the decline of the year, when the atmosphere is losing both heat and water," the variations of the two instruments often correspond. The same observation as to want of distinctness of effect in the different periods of the moon's age applies to the account given of the proportion of rain during the different phases. In some years the effects appear very considerable, in others less so, and in some they seem reversed. In general, however, it appears to hold, that the temperature is increased and the rain diminished during the periods of new and full moon, and the temperature lessened and the rain increased during the first and third quarters. These effects, as we have already remarked, are immediately produced by the particular classes of winds respectively prevalent in the different phases of the moon; and a reference to the connexion of the different winds with rain, noticed in a former page, will explain this fact. "Not but that there are seasons (our author observes) when the predominant solar influence is exerted to a degree which renders these Lunar changes of small consequence; and when, in spite of the various aspects of our attendant planet, we are drenched with rain or parched with drought, for months together." (P. 239.) With respect to the different influence of the moon according to her particular declination, we have already noticed the effects produced on the mercury in the barometer. The following paragraph, which we select on account of its brevity, will give a slight view of the further effect of the moon's declination on rain and temperature; and also explain the author's idea of the cause of these particular effects. "A general tendency in the Northern atmosphere to come over us (that is, to flow in mass towards the South), while the moon is far South, may be admitted as a cause why the barometer at this time is above the mean, the temperature about or below it, and the rains in small quantity. As the moon comes North again, the air returning from the South causes increased temperature; it brings also a great increase of vapour, and the heat evolved during the condensation of this, may possibly be the means of the greater elevation of the mean temperature at this time in the wet, than in the dry year. Something must, however, be attributed, in this case, to the actual translation of more of the tropical air into these latitudes in a wet season." (P. 268.) "On the whole it may be inferred that the winds in a temperate alatitude like our own, after escaping from the tropical vortex, become subject, in winter more especially, to the moon; and that their tendency is to follow her path, or the moveable point of greater rarefaction which she marks out for them." (Vol. ii. p. 276.) The above is a brief enumeration of the principal facts observed by Mr. Howard respecting the moon's influence on the atmosphere. These, it may be thought by some, are neither so numerous nor so clear as could be wished. They are, nevertheless, highly interesting; and if the amount of their value was nothing more than that of furnishing an index and a stimulus to future inquirers, they must be considered as extremely important. So far from being disposed to comment on the paucity of facts which he has been able clearly to demonstrate, we ought to be surprised rather, in this the very infancy of the study, that he has succeeded in doing so much. For, as he justly and judiciously observes, "if the moon's attraction be really the principal cause of those variations in the atmosphere which cannot be traced to the influence of the superior planet, the mode of operation of this attraction may be very simple, at the same time that, considering the complicated nature of the lunar orbit, and the perpetual interference of the sun's varying power, its manifestations in any given temperate climate may prove a very difficult subject to investigate." (P. 271.) Near the conclusion of the volume, Mr. Howard departs from his usual cautious tract of the mere generalization of facts, and, under the modest title of conjectures, gives a beautiful and interesting view of what he conceives to be the general theory of the winds and weather over the whole globe. To this we must be contented with simply referring the reader; and shall only mention two of these which he himself seems to regard as entirely conjectural. The first of these is the "possible case that the full moon, with a surface intensely heated by the sun, may radiate a portion of heat to the colder parts of the earth's surface towards the poles; more especially when in her extreme North and South declination; and, on the contrary, that the new moon, having become proportionally cold on the surface opposed to us, may receive by radiation from the earth, and more especially from the tropical regions, a compensating degree of heat."+ The second conjecture is, whether the fact, of that portion of Alluding to the years 1807 and 1816, which he had been comparing.—Rev. + The truth or falsehood of this conjecture, we think, might easily be set at rest by an extension of Mr. Leslie's most ingenious instruments, the Photometer and Ethrioscope-Rev. the moon's disk not illuminated by the solar rays being sometimes very distinctly visible to us, and at other times not at all, when precisely in the same position, (namely in the interval between the new moon and first quarter,) may not be explained by supposing the reflexion of light from our planet (which alone can account for the effect at all) being augmented, at those particular times, by an extensive surface of snow on the Northern American continent? Such is an imperfect outline of the valuable work of Mr. Howard; in submitting which to our readers we feel satisfied in the conviction, that our labour in its construction will be neither altogether useless to them nor to ourselves. We have presented to them in detail a vast number of highly interesting and important facts, some of which, we verily believe, point to a new and most attractive field of philosophical inquiry, fruitful in discoveries, and only awaiting the hand of cultivation. Many obvious remarks arise in our minds in contemplating the mass of information submitted to the reader ;-but, while we consider the great general value of the work, we feel no disposition to point out trivial deficiencies, or dwell on minute errors; and the consciousness of having enriched our pages with more than a usual portion of valuable matter, furnishes us with a sufficient excuse for not enlarging further on its merits. Just as we were about to complete the above article for our printer, by a curious coincidence we had put into our hands the little work on the Climate of Penzance, the title of which we have placed at the head of our review, after that of Mr. Howard's Treatise. As this publication of Dr. Forbes is strictly of that class which we have commended, viz. a faithful history of the weather of a particular district, deduced, by the simple process of generalization, from a long continued series of observations; and as it appears to us to be a simple and good model for the construction of such local histories, we should have willingly devoted a few of our pages to a review of it, had we not already occupied so many with the same subject. We must, therefore, content ourselves with noticing one or two particulars, which may give our readers some idea of the very peculiar climate of Penzance, and, at the same time, illustrate some of the general principles alluded to in the preceding article. From the situation of Penzance, within a few miles of the promontory denominated the Land's End, which is projected, as it were, into the Atlantic from the rest of England, by the long and narrow peninsula of Cornwall, great peculiarity of climate might be expected in this district, when compared with the interior and northern counties. It must possess all the habitudes of a small island, in its own particular latitude and longitude; in other words, it must exhibit nearly the same weather as is to be found on the surface of the neighbouring ocean. The most striking feature of the climate of this district seems, accordingly, to be, the remarkable equability of its temperature. With the view of placing this in as conspicuous a light as possible, we shall here transcribe from the works of Mr. Howard and Dr. Forbes, first, the mean temperature of the twelve months at London and Penzance; and, secondly, the extreme temperature of each month for the whole series of years (viz. ten for London, and fourteen for Penzance). London London 1.-MEAN TEMPERATURE. |Jan. Feb. Mar. Apr. May June July Aug. Sep. Oct. Nov. Dec. 34 39 41 46 55 58 62 60 62 66 61 56 50 40 37 61 58 53 46 43 2.-EXTREME TEMPERATURE.* Jan. Feb. Mar. Apr. May June July Aug. Sep. Oct. Nov. Dec. Max. 56 57 73 80 87 88 96 83 85 73 62 Penzance Min. 19 26 28 32 42 45 14 64825 78 74 68 69 22 It appears, in like manner, from documents contained in Dr. Forbes's essay, that the temperature of Penzance retains the same proportional superiority in the colder months over all the places usually esteemed the mildest in our island; for instance, the sea coast of Devonshire, the Isle of Wight, Clifton, &c.; a fact which well accounts for, and justifies, the resort of consumptive invalids to the western extremity of Cornwall. In thirteen years the thermometer, at 7 a. m. at Penzance, has only been thirty-seven times below the freezing point; consequently frost is stated to be of rare occurrence; and the exercise of skating entirely unknown among the young men of the place. The average number of days in the year on which snow falls is very little more than two and a half; and out of the fourteen years, four are recorded on which no snow fell. As the most unequivocal proofs of the peculiar mildness of the winters, Dr. Forbes, at the end of his paper, gives lists of the exotic and indigenous plants growing in the vicinity of Penzance; among which * As the minimum column for Penzance gives only the minimum at 7 a. m. it will probably occasionally happen that that stated is above the true minimum of some of the months. we observe several which we have never been accustomed to see beyond the walls of a green-house. Two crops of potatoes are yearly produced in the open grounds. The range of the barometer, as also its mean altitude, at Penzance, is considerably less than at London. ART. XI.-Memoirs from 1754 to 1758. By James Earl Walde grave, K. G. one of His Majesty's Privy Council in the Reign of George II. and Governor to the Prince of Wales, afterwards George III. 4to. 4to. pp. 176. Murray. London, 1821. THE book now before us possesses intrinsic merits, which might have rendered its external decorations unnecessary. The style is extremely neat; it is even spirited and elegant; the topics which are brought forward are explained concisely; we are never encumbered either with words which are not necessary for the developement of the ideas, or with ideas which are not necessary to an accurate comprehension of the subject matter. Every page bears marks of the man of good sound sense, matured by meditation, and trained in the real business of life. There is no ambition of brilliancy, or of wit, or of any species of literary ornament. The author seems to have had no object beyond that of telling what he knew in simple language; and if this simplicity is sometimes combined with keen indirect sarcasm, the infusion seems to take place almost without his consciousness. Memoirs are a class of productions, in which our language, at least when compared with the French, is not very rich. We have never been much disposed to envy our neighbours this species of wealth; for their memoirs, in general, are little else than dull novels or duller gazettes. Even in the few works of this description, in which valuable information or skilful delineation of character is to be found, the grain is lost amid the immensity of chaff. Trifles and important transactions are detailed with equal care. Whatever was an interesting subject of conversation at the time; the anecdotes for instance, of private scandal, or the minutiae of a court ceremonial, are deemed as worthy of the attention of posterity, as events on which great systems of policy depended. The memoirs now before us are free from all such reproach; they relate exclusively to public men and public events; and treat of the one or the other, only so far as they are entitled, by having had an influence on the administration of the national concerns, to the attentive consideration of posterity. |