3000 velocity due to a head of pressure of feet, or 8 x per second. Whenever a hard shower takes place from a lofty cloud of moderate diameter, such will be the effect at the surface of the earth. For as the perpendicular diameter of a cloud, which produces a very hard rain, must be great, the drops of rain must descend from a great height, and will enter this lower stratum of air very cold, sometimes frozen; the effect will manifestly be as stated above. This explanation will apply most satisfactorily to the gale which took place at Portsmouth and Middletown, from north-west, and in New Jersey, near Amboy, from the north-east, on the morning of the 20th of June, after a most violent rain, which fell on the evening and night previous, in the eastern part of New York, all round Albany. The wind in all these places blew outwards from, where the rain had fallen. The air in New Jersey was described as piercingly cold, and at Portsmouth, New Hampshire, it was fourteen degrees colder than on the day before at the same hour. The reader will observe that the clouds below at Philadelphia continued to move from the south-west. on the 20th of May, after the wind changed round to the north-west, while at the same time an upper stratum of clouds was coming from the north-west. The whole phenomena of this storm, and others of moderate diameter, where the cloud does not descend very low, as it did on the 19th of June, will be clearly comprehended by supposing that there is an inward motion of the air at the lower part of the cloud, an upward motion in the cloud, and an outward motion in the upper part of the cloud, as indicated by the arrows in the wood-cut. This upward motion also, if it could be shown how it is effected, would account for the condensation of the vapour into rain by the diminution of temperature resulting from diminished pressure, which it is known amounts to at least one degree Fahr., in the case of dry air, for every hundred yards of ascent. The wood-cut is intended to represent only those storms of moderate size in which the cloud is of sufficient height to let the air below become so cooled as to produce an outward motion at the surface of the earth. There are, however, two other cases in nature, in which the wind at the surface of the earth blows inwards. First, when the cloud reaches down to the surface, or near the surface of the earth, as in the Brunswick spout. Second, when the cloud is of very wide extent, and the rain general; in which case the air to supply the storm with vapour or steam, cannot find room to enter under the cloud without carrying in with it all the air between the cloud and the surface of the earth. These three kinds embrace all the varieties of storms in nature. Now as the characters of these three kinds of storms are very distinct, and as it will be very convenient hereafter to speak of them separately, I propose to call that kind which is very narrow, and having the wind blowing inwards at the surface of the earth, primary; that one which is of mean size, and has the wind blowing outwards at the surface of the earth, secondary; and that which is very wide, and has the wind blowing inwards at the surface of the earth, tertiary. The choice of these names arises from the theoretic probability that all storms commence with the first character, pass into the second, and terminate with the third. JAMES P. ESPY. Review of Mitscherlich's Compendium of Chemistry, with remarks on the method of teaching Chemistry. By JAMES C. BOOTH. FOR THE JOURNAL OF THE FRANKLIN INSTITUTE. Among the votaries of any science, a lively interest is naturally felt in the publication of works connected with that science; a feeling greatly enhanced by the circumstance of their proceeding from men of high reputation. This is more particularly the case with chemistry, which is daily increasing under the hands of its followers, by the accumulation of new and important facts, and by the proposal of new theories to account for the phenomena. Numerous works in this science, of greater or less comparative value, are yearly brought before the tribunal of public opinion, and yet there are but few which do not either wholly fail of success, or which have more than a limited circulation. The cause of this is not so much an igno rance of theory on the part of the author, as the want of sufficient practical knowledge to enable him to put much of his theory to the test. As chem. istry is a science of facts, so it cannot be learned without seeing them, nor taught without being able to exhibit them; hence it is that he who has experimented himself, is better able to describe the results of his operations, than he who describes phenomena of which he has only heard or read; for the former gives the more striking impression, which the experiment made on him, the latter the impression as derived from a description. Another cause operates to render the great majority of works in this, as in other sciences, unsuccessful; they are destitute of uniformity of execution. Too few authors, in commencing a work, are themselves aware of their object, or if they be aware of it, pursue it with that uniform and steady aim which is absolutely necessary to its complete success; hence many otherwise excellent treatises are rejected for this reason alone, while others of inferior merit, but exhibiting uniformity of purpose, rise above and even supersede them. "Whoever would please every one, pleases no one," does not lose its force by repetition, for there is no single work on chemistry suited to every class VOL. XVII.-No. 6.-JUNE, 1836. 37 3000 velocity due to a head of pressure of feet, or 8 x per second. Whenever a hard shower takes place from a lofty cloud of moderate diameter, such will be the effect at the surface of the earth. For as the perpendicular diameter of a cloud, which produces a very hard rain, must be great, the drops of rain must descend from a great height, and will enter this lower stratum of air very cold, sometimes frozen; the effect will manifestly be as stated above. This explanation will apply most satisfactorily to the gale which took place at Portsmouth and Middletown, from north-west, and in New Jersey, near Amboy, from the north-east, on the morning of the 20th of June, after a most violent rain, which fell on the evening and night previous, in the eastern part of New York, all round Albany. The wind in all these places blew outwards from where the rain had fallen. The air in New Jersey was described as piercingly cold, and at Portsmouth, New Hampshire, it was fourteen degrees colder than on the day before at the same hour. The reader will observe that the clouds below at Philadelphia continued to move from the south-west. on the 20th of May, after the wind changed round to the north-west, while at the same time an upper stratum of clouds was coming from the north-west. The whole phenomena of this storm, and others of moderate diameter, where the cloud does not descend very low, as it did on the 19th of June, will be clearly comprehended by supposing that there is an inward motion of the air at the lower part of the cloud, an upward motion in the cloud, and an outward motion in the upper part of the cloud, as indicated by the arrows in the wood-cut. This upward motion also, if it could be shown how it is effected, would account for the condensation of the vapour into rain by the diminution of temperature resulting from diminished pressure, which it is known amounts to at least one degree Fahr., in the case of dry air, for every hundred yards of ascent. The wood-cut is intended to represent only those storms of moderate size in which the cloud is of sufficient height to let the air below become so cooled as to produce an outward motion at the surface of the earth. There are, however, two other cases in nature, in which the wind at the surface of the earth blows inwards. First, when the cloud reaches down to the surface, or near the surface of the earth, as in the Brunswick spout. Second, when the cloud is of very wide extent, and the rain general; in which case the air to supply the storm with vapour or steam, cannot find room to enter under the cloud without carrying in with it all the air between the cloud and the surface of the earth. These three kinds embrace all the varieties of storms in nature. Now as the characters of these three kinds of storms are very distinct, and as it will be very convenient hereafter to speak of them separately, I propose to call that kind which is very narrow, and having the wind blowing inwards at the surface of the earth, primary; that one which is of mean size, and has the wind blowing outwards at the surface of the earth, secondary; and that which is very wide, and has the wind blowing inwards at the surface of the earth, tertiary. The choice of these names arises from the theoretic probability that all storms commence with the first character, pass into the second, and terminate with the third. JAMES P. ESPY. Review of Mitscherlich's Compendium of Chemistry, with remarks on the method of teaching Chemistry. By JAMES C. BOOTH. FOR THE JOURNAL OF THE FRANKLIN INSTITUTE. Among the votaries of any science, a lively interest is naturally felt in the publication of works connected with that science; a feeling greatly enhanced by the circumstance of their proceeding from men of high reputation. This is more particularly the case with chemistry, which is daily increasing under the hands of its followers, by the accumulation of new and important facts, and by the proposal of new theories to account for the phenomena. Numerous works in this science, of greater or less comparative value, are yearly brought before the tribunal of public opinion, and yet there are but few which do not either wholly fail of success, or which have more than a limited circulation. The cause of this is not so much an igno rance of theory on the part of the author, as the want of sufficient practical knowledge to enable him to put much of his theory to the test. As chem. istry is a science of facts, so it cannot be learned without seeing them, nor taught without being able to exhibit them; hence it is that he who has experimented himself, is better able to describe the results of his operations, than he who describes phenomena of which he bas only heard or read; for the former gives the more striking impression, which the experiment made on him, the latter the impression as derived from a description. Another cause operates to render the great majority of works in this, as in other sciences, unsuccessful; they are destitute of uniformity of execution. Too few authors, in commencing a work, are themselves aware of their object, or if they be aware of it, pursue it with that uniform and steady aim which is absolutely necessary to its complete success; hence many otherwise excellent treatises are rejected for this reason alone, while others of inferior merit, but exhibiting uniformity of purpose, rise above and even supersede them. "Whoever would please every one, pleases no one," does not lose its force by repetition, for there is no single work on chemistry suited to every class VOL. XVII.-No. 6.-JUNE, 1836. 37 of readers or of students, nor can it indeed be anticipated in a science em. bracing such an infinite number of facts, and such a variety of objects. What interest does the miner, or the smelter of metals take in organic chemistry? Of how little real utility to the pharmaceutist or manufacturing chemist are discussions relative to the subtle theories of the science? Is it necessary for the purely theoretic chemist to be acquainted with all the details of the manufacturer? How little has the student, when commencing, to do with all these? Lastly, where is the chemist who can embrace them all with the same energy as when devoted to one only? Therefore I contend for unity of purpose, and uniformity of execution, and I think the answers to the foregoing questions will be found conclusive. A work on chemistry has lately appeared to which the name of its author alone would ensure success, though not perfectly free from the faults I have above endeavoured to point out; for notwithstanding these, it possesses merits of a peculiar kind, entitling it to consideration. Whoever would call over the names of chemists of celebrity, of the present day, and omit in his catalogue that of Professor Mitscherlich, of Berlin, the founder of the doctrine of isomorphism, would do great injustice to him and to the school to which he belongs. For although this doctrine be not fully developed, it has nevertheless been resorted to with success, for correcting for mer errors, and strengthening certain theories, and promises to become an important agent in disclosing the hidden operations of nature. All that we have hitherto known of Mitscherlich are a few treatises, through the medium of their French translations, and we are now introduced to him as the author of a "Manual of Chemistry." I propose giving a sketch of the subjects contained in the first part of the first volume, (for the whole has not yet appeared) and would wish to draw the attention of the reader at the close, to a few remarks on an important subject, viz. the method of instruction to be pursued, in communicating the facts of chemistry to the uninitiated. The work commences without preface or introduction, the first page containing an enumeration of the elements with which we are acquainted, and the second thus unceremoniously introducing oxygen to our notice: "If red oxide of mercury be heated in a retort, the neck of which passes through a cork in one opening of a receiver, then, through a tube fitted in another opening, bubbles of air will pass and displace the water contained in an inverted cylinder." This is accompanied by a wood cut representing the apparatus, and a detailed description of the entire operation. A few deductions are then drawn from the experiment, viz: that there is a metallic body liquid at common temperatures; that there is a gaseous body differing in its properties from common air, this being shown by transferring a part of the gas into smaller vessel, and holding a cinder of wood in it-that these two are held together by a certain power, which is termed affinity, and similar conclusions, such as a reflecting student might be supposed to make for himself. The same experiment is then supposed to be arranged in such a manner, that the resulting metal and gas may be weighed, from which the conclusion is drawn, that the red oxide is composed of certain quantities of the two substances alone, so combined that their individual properties cannot be detected, and in this simple manner the first clear views of the effects of affinity are communicated. The method of preparing oxygen for practical purposes, from the black oxide of manganese, is next minutely described, together with the iron retort and gas-holder employed in the operation. A large number of experi ments are exhibited by Professor Mitscherlich before his class, which are |