We are not altogether willing, even yet, to leave the subject, without addressing a word to those who have it in their power with convenience to assist an antiquarian publication of this nature. Mr. Pitcairn would not, probably, thank us, were we to make this expostulation in the tone of the recruiting sergeant, who assures the public, that only a very few young gentlemen of the most irreproachable habits are wanted to complete the gallant regiment for which he beats up. We may, however, observe, that the two associations of the Bannatyne and Maitland Clubs have done all which can be expected from societies so constituted, in encouraging the present laborious and expensive work; and it will be but fair in those who call loudly upon them to give the world the benefit of their private presses, to show, on an occasion like the present, that they really set a value upon such things-since, whether the exclusive system practised by these institutions is or is not the most advantageous that might be devised, it certainly has arisen from the carelessness and coldness with which almost all insulated attempts of this nature have recently been suffered to fall to the ground. ART. VI.-A Treatise on Sound. By J. F. W. Herschell, Esq., F.R.S. London and Edinburgh,. &c. (In the Encyclopædia Metropolitana.) Lond. 1830. A WORK on any branch of natural philosophy from the pen of Mr. Herschell must at all times be an object of interest to the philosopher as well as to the general reader, who is sufficiently prepared for its perusal: his mathematical acquirements, his acquaintance with modern discovery, his powers of illustration, and the originality of his views, qualify him in a peculiar manner for writing a systematic account of any of the physical sciences. The Treatise on Sound,' of which we propose to give some account, is marked with all these characteristics of his powerful mind; but we regret to add, that it is fitted only for the perusal of the mathematical philosopher; and though the general reader will discover, here and there, portions which he is capable of understanding, yet he will find himself baffled at every step by profound views, and by the perpetual recurrence of mathematical formulæ. In every other country but England, a work like the present would have had many readers among the upper and the middle ranks of society; but so great has been the decline of mathematical knowledge, and so completely has science been excluded from the list of accomplishments which qualify for public life, that that there is scarcely an individual, not professionally scientific, who is capable of understanding or of appreciating Mr. Herschell's labours. Even those who have successfully pursued the admirable course of scientific instruction which exists at Cambridge, and, to a certain extent, at Oxford, will be found to have forgotten their early acquirements, and to have thrown aside their science as a weight which would only incumber them in the race of professional ambition. In the times that have gone by, science was more prevalent among the educated classes, and was honoured with more patronage among the upper ranks. In every part of the kingdom there were found men of wealth and title, who, though not profoundly scientific, were yet zealous amateurs and active cultivators of popular and practical science: they were the patrons of the village philosopher and the village artist. With their telescopes, their solar microscopes, their electrical machines, and their airpumps, they displayed to their visitors the more striking phenomena of the physical world. A beneficial respect for science was thus maintained within the pale of their influence, and those who were not admitted to see its wonders, heard of them at secondhand, and strove to fathom those mysteries of nature which amused the baron in his hall, and supplied wealth with one of its most elegant luxuries. This race of opulent and noble amateurs is now nearly extinct; and in the extended list of English, Scottish, and Irish nobility, we can remember only the names of five * individuals who dignify their rank by scientific attainments. But not only has science ceased to become an object of ardent pursuit and of enlightened patronage-its grandest and most intelligible results have ceased to be received as demonstrated truths, and philosophers are often regarded as little better than jugglers, who impose upon popular credulity, and invest with the dignified name of general laws what are only deductions from their own plausible speculations. It is not easy to devise a cure for such a state of things; but, in addition to some legislative enactments, the nature of which has been generally stated in a former Number,† the most obvious remedy is to provide the educated classes with a series of works on popular and practical science, freed from mathematical symbols and technical terms, written in simple and perspicuous language, and illustrated by facts and experiments which are level to the capacity of ordinary minds. If a general taste should thus be created for popular science, our reviews, magazines, aud jour The Lord Chancellor Brougham, the Duke of Buckingham, the Marquis of Northampton, the Earl of Minto, and Lord Oxmantown; we hope our catalogue is not quite complete! † No. 86. nals nals would be induced to devote a portion of their pages to the development and simplification of modern discoveries, and philosophers of high name would not scruple to add to their more permanent reputation the contemporary fame of bringing within the grasp of their less gifted countrymen the beauties and the wonders of the material universe. As there are few persons who have any idea of the delightful and instructive reading with which they would thus be supplied, we propose to devote the following pages to a popular account of the discoveries which have been made on the subject of Sound,' following the train of inquiry pursued by Mr. Herschell, and enlarging on several topics which he has either briefly discussed or entirely omitted. The object of Mr. Herschell's treatise is to explain the nature and production of sound,-the laws of its propagation through various media (such as air, water, and solid bodies) which convey it to our ears, the manner in which it acts on these organs, the modifications of which it is susceptible in speech, music, or in inarticulate and unmeaning noises,—and the natural and artificial means of producing, regulating, or estimating sounds. That sound is conveyed to the organ of hearing through the air is a fact which has been known from the remotest antiquity; but so little notice had this interesting subject excited, that it was not till the beginning of the last century that it was proved by experiment that the air is the vehicle by which sounds are conveyed, and that without its influence nature would be buried in the deepest silence. This important fact was first established by our countryman, Mr. Hauksbee, by suspending a bell in a large glass vessel. When the air was drawn out of the vessel, and the bell rung, the sound gradually grew fainter; and when the vessel was completely emptied of its air, the sound of the bell could no longer be heard, even though the ear was held close to the vessel. Upon re-admitting the air into the vessel, the sound of the bell was again heard; and it became louder and louder, and acquired its original strength, when the vessel was filled with air which communicated with that of the atmosphere. When more air was forced into the glass vessel, or when it was filled with denser or heavier air than that of the atmosphere, the loudness of the sound was found to increase with the density or heaviness of the air. Hence we discover the cause of that deep silence which reigns in the elevated regions of the globe, and which, when combined with their habitual solitude, produces an impression on the mind at once grand and awful. The busy hum of men, of their voices and their deeds, is gradually extinguished as the traveller rises above the level of human affairs; the ocean's deep swell, and the fitful murmurs of the falling stream, are soon lost in their distance; and even the sounds of animated nature, which, during the stillness of night, and in the pure atmosphere of tropical climates, fall with such clearness and solemnity upon the ear, die away in the attenuated air. Thus removed from the region of life and motion, the travellers begin to experience between themselves other effects of their high elevation. Not only are the sounds by which they hold communication with each other enfeebled, and even incapable of being heard at moderate distances, but the muscular energy by which they utter them suffers a considerable diminution; and, with their powers of speech and their powers of hearing thus strangely modified, they can scarcely avoid feeling as if they were already on their way to the land of their destiny, and as if the functions of their corporeal nature, as well as the powers of the elements, had begun to undergo the transformation of a more spiritual existence. But though sounds of ordinary intensity are thus weakened at great heights above the sea,-though Saussure found that a pistol fired on the top of Mont Blanc gave a report no louder than that of an Indian cracker,-yet at much greater elevations than that of the highest mountains the air is still able to transmit to the regions below sounds of great power and intensity. At heights in an atmosphere where the air is three thousand times more rare than that which we breathe, the sounds of meteors have been propagated down to the earth. The meteor of 1714, whose height was at least thirty-eight miles when it passed across Italy, was heard to make a hissing sound, like that of artificial fireworks: at Leghorn it gave a loud report, like that of a great cannon, terminating in a sound resembling the rattling of a cart of stones, which Montanari describes as lasting about the time of a Credo.' The meteor of 1719 was still more formidable by the sounds which it emitted. In Devonshire and Cornwall its sound was that of a broadside of cannon, followed by the rattling noise of musketry: the whole air experienced a violent concussion; windows and doors, and even houses, shook; at Tiverton it threw a lookingglass out of its frame and broke it; and these effects were the result of an explosion at the height of sixty-seven miles above the earth. The transmission of sound through the atmosphere does not take place instantaneously. Every person has observed that the flash of a gun is seen before the sound of the discharge is heard, and that the interval between them becomes longer as the gun is more distant. The lightning, too, is always seen before the thunder commences, and the interval is often very considerable. The The sound of the great meteor of 1783 was not heard till ten minutes after it disappeared. Although the velocity of light is infinitely greater than that of sound, yet philosophers had determined the speed of the former long before they had measured that of the latter. This arose principally from the want of a proper method of measuring small portions of time, which modern philosophers have been so fortunate as to possess. One of the instruments for this purpose, called a Chronograph, and invented by M. Rieussec, is a sort of timepiece, one of whose hands performs a revolution round the dialplate every second. By suddenly pressing a lever at any given instant, the extremity of the hand is made to touch the dial-plate, and leave a drop of printers' ink, without its own motion being in any way interrupted. By this, or similar contrivances, it was found practicable to determine the interval between the flash and the sound of a gun with such nicety as to render the measurement of the velocity of sound a comparatively easy experiment. Since the year 1660, when the experiment was first made by the Florentine academicians, various determinations of the velocity of sound have been published; but by taking a mean of those which have been made with all the aids of modern science, it appears that, in dry air and at the freezing temperature, sound travels at the rate of 1090 feet, or 363 yards, in a second; and that at 62° of Fahrenheit, it travels 9000 feet in eight seconds, 123 British standard miles in a minute, and 765 miles in an hour. Hence, as Mr. Herschell has calculated, sound moves with the same velocity as a point of the earth's surface in latitude 42° 20′ 40′′: so that, if in that latitude a gun be fired at the moment any star passes the meridian, the sound will reach any other place exactly west of it at the same instant of time that the star reaches its meridian. The transmission of sound from one place to another is often singularly obstructed by the state of the air, or of the ground over which it passes. Fogs, and falling rain and snow, produce a very marked effect, which must have been noticed by the most careless observer; but the strangest effect is produced by a deep coating of new fallen snow. We have heard an officer describe a remarkable fact of this kind, which he observed during the American A river separated the British and American lines, and the outposts were so near that the form of individuals could be easily recognised. His attention was accidentally directed to a drummer who began to beat his drum. The active movement of his arms was distinctly seen, but not a single note reached the ear of the observer. A coating of new fallen snow had totally obstructed the sound, and produced in perfection the phenomenon of the muffled drum. The very opposite effect, however, is occasioned war. by |