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Popular Science Monthly/Volume 5/June 1874/Miscellany

MISCELLANY.

A Science Minister for England.—There is an agitation now going on in England for the appointment of a responsible government minister, whose duty it shall be to look after the interests of science and scientific research and education, and to take charge of the scientific institutions of the country. A writer in the Times, Colonel Strange, whose views are approved by Nature, calls attention to the fact that, though "there is more individual enterprise in England than in any country in the world," yet the English are being rapidly outstripped by other nations. At present, the various scientific institutions maintained by the state are under no less than seven different governmental departments, all of which have other matters besides science to attend to. The writer names six observatories, of which one, Greenwich, is under the Admiralty; another, Edinburgh, under the office of Works; a third, at the Cape of Good Hope, under the Colonial office; and the rest under the India office. The other departments of state which assume to direct scientific work are the Privy Council and Board of Works, and Board of Trade. Colonel Strange favors the creation of a Science Minister, under whose control all these scientific institutions shall be placed. "Let this be done," says he, "and we should cease to witness the farce of consulting the Chancellor of the Exchequer about observing eclipses of the sun, the prime-minister about scientific arctic expeditions, and the Treasury about tidal reductions. We should perhaps, too, then perceive that overworked law-officers are not the best managers of a great, or what should be a great, technical museum, and that fifty irresponsible gentlemen, however eminent individually, ought not to be intrusted with the grandest collection of art and natural history in the world."

 

The Acoustic Properties of the Atmosphere.—The coasts of the British Isles are exceedingly beset with fogs, which make navigation in their vicinity a very dangerous business. During a period of ten years these fogs were the cause of 273 shipwrecks, many of which were attended with serious loss of life. As signals in thick weather, lights are almost worthless; sounds have, accordingly, been substituted, and instruments for producing them, such as bells, fog-horns, steam-whistles, etc., have been set up and employed at numerous stations. But it has been observed that the distances at which these sounds could be heard were extremely variable; that while at one time they would give warning seven or eight miles away, at another they were inaudible at half the distance, and perhaps totally useless for the purpose intended.

The authorities last spring requested Prof Tyndall to look into the matter, which he did, and, as is usual with him, when he undertakes an inquiry, with interesting and valuable results. Selecting the South Foreland Cliff, in the Straits of Dover, as the site of operations, he began a series of experiments to test the distances at which various sounds could be heard. The instruments used for producing the sounds were, trumpets sounded by air, whistles sounded by steam, the steam-siren, and cannon. The observations were continued at intervals from the 20th of May last to the 25th of November. At different times sounds of like intensity were heard at widely-varying distances. For example, a sound that at one time could be heard only two miles, could at another time be heard twelve miles. On one occasion the sound of the steam-siren was heard fifteen miles. On the morning of June 3d, the sky being of a stainless blue, and the sea calm, the sound of a cannon could not be heard beyond two miles, and a "mortar fired with a three-pound charge yielded only a faint thud; it was mere dumb-show on the Foreland." The air was optically clear, but opaque and impenetrable to sounds. On other occasions, during fog, and driving rain, the sounds could be heard at various distances, as four, five, seven, and nine miles; and once, when the air was hazy, they were heard twelve and three-quarter miles. The inference is, that the transmission of sound through the atmosphere is not affected by fogs and rain; the air during their prevalence may be opaque to sound, but not on that account. The movement and arrest of sound in the air depend on other conditions than the mere presence of fog or rain, and these conditions may exist when the atmosphere is wonderfully clear to the eye. What, then, becomes of the enormous volumes of sound produced by cannon and the steam-siren, seeing that they are neither transmitted nor annihilated? In order to determine this question, Prof. Tyndall and his companions took a position on the shore overlooking the sea, and there for the first time demonstrated by experiment "the reflection of sound from aerial surfaces. From a perfectly clear air the sounds came back in echoes. They reached us as if by magic from absolutely invisible walls." Now, what are the conditions which thus intercept the sound-waves? The phenomenon is clearly due to a non-homogeneous atmosphere produced by inequalities of temperature, and the unequal distribution of vapor. "As I stood upon the deck of the Irene," says Prof. Tyndall, "pondering the question, I became conscious of the exceeding power of the sun beating against my back and heating the objects near me. Beams of equal power were falling on the sea, and must have produced copious evaporation. That the vapor generated should so rise and mingle with the air as to form an absolutely homogeneous mixture, I considered in the highest degree improbable. It would be sure, I thought, to streak and mottle the atmosphere with spaces in which the air would be in different degrees saturated.... At the limiting surfaces of these spaces, though invisible, we should have the conditions necessary to the production of partial echoes and consequent waste of sound." This philosophical explanation Prof. Tyndall was able to verify. On one occasion, when the air was opaque to sound, a cloud arose and threw its shadow over the sea. Some increase in the intensity of the sounds was noticed; but, with decline of the sun, it was more obvious, until at length the signal-sounds were heard at a distance of twelve and three-quarter miles, when at first they were inaudible at two miles. The increase of distance at which the sounds were distinctly heard was gradual with decline of the sun, or, what is quite obvious, with increase of homogeneity of the atmosphere. This was fully shown on another occasion, when, during a violent rain, the transmission of sounds was greatly increased, so that they could be heard more distinctly at seven and one-half miles than at five miles previous to the storm.

 

The Anderson School at Penlkese.—The Anderson School of Natural History will open this year on Tuesday, July 7th, and close on Saturday, August 29th. During the session. Prof. Mayer, of the Stevens Institute, Hoboken, will deliver a course of lectures on Physiological Physics. Mr. Theodore Lyman, of the Cambridge Museum of Comparative Zoology, will give a few lectures on Pisciculture. Lectures will also be delivered by Dr. W. S. Barnard, of Ithaca, N. Y., on Protozoa; Prof. Jordan, of Appleton, Wis., will take charge of the instruction in Marine Botany. Mr. Alexander Agassiz will have charge of the instruction on Radiates and Embryology; Dr. A. S. Packard, Jr., of Salem, Mass., on Articulates; Prof. B. G. Wilder, of Cornell, on Vertebrates; Prof. E. S. Morse, of Salem, and Prof. C. E. Hamlin, of the Museum of Comparative Zoology, on Mollusca; Mr. T. W. Putnam, Director of the Peabody Academy of Science, on Fishes; Mr. Edwin Bicknell, of the Museum of Comparative Zoology, on Microscopy. Instruction in Drawing will be given by Mr. P. Roetter, of the Museum of Comparative Zoology. Dr. Packard and Mr. S. W. Garmon will take charge of the dredging expedition, and the laboratories will also be under the supervision of Mr. Garmon.

 

Scientific Apparatus.—While it cannot be questioned that the popular demand in this country for appliances with which to illustrate the first principles of physical science is well met by several makers of philosophical instruments in this and other cities, it is still true that, in the higher branches and grades of scientific illustration, our chief dependence for efficient apparatus is upon English, French, and German makers. In the two great departments of Electrics and Optics this is especially observed, and we take pleasure in commending to the notice of professors and teachers of science the card of Mr. Browning, of London, in our advertising page this month. Mr. Browning is an honored Fellow of the Royal Astronomical Society of England, and, what is more to the present purpose, he is the successful maker to the Royal Society, and to the leading English observatories, of the instruments they employ in their great and varied work. In the construction of spectroscopes of every sort he has, perhaps, no equal, certainly no superior.

 

Soaring and Sailing of Birds.—Mr. Belt, describing the movement of a pair of black vultures sailing on the wind, says: "Like all birds that soar, both over sea and land, when it is calm the vultures are obliged to flap their wings when they fly; but when a breeze is blowing they are able to use their specific gravity as a fulcrum, by means of which they present their bodies and outstretched wings and tails at various angles to the wind, and literally sail. How often when becalmed on southern seas, when not a breath of air was stirring, have I seen the albatross, the petrel, and the Cape-pigeon, resting on the water, or rising with difficulty, and only by the constant action of their long wings able to fly at all! But when a breeze sprang up they were all life and motion, wheeling in graceful circles, now presenting one side, now the other to view, descending rapidly with the wind, and so gaining velocity to turn and rise up again against it. Then, as the breeze freshened to a gale, the petrels darted about.... poising themselves upon the wind with as little effort as a man balances himself upon his feet."

 

An Aged Pelican.Land and Water contains an interesting "obituary notice" of Jack the Pelican, for upward of forty years an inhabitant of the Dublin Zoological Gardens. This line specimen of the genus Anser was presented to the gardens in 1831, being then full grown, and supposed to be seven or eight years old. Jack was generally about the first specimen which was introduced, or rather introduced himself, to the notice of visitors, as he was seldom shut up in a cage, but walked or waddled about where he pleased. He usually treated strangers with sovereign contempt, hardly deigning to get out of their road; but when seized, and his beak opened to show his curious little cleft tongue, which lay at the bottom of the pouch, under the bill, his eye, usually a splendid ruby, or rather carbuncle color, got red as a coal, with anger, at the indignity. His plumage was always in the most beautiful order and the most brilliant white, except about the head, where the soft, downy hackles assumed a pinky hue. Curiously enough, he never went into the water, except occasionally for the purposes of ablution, when he would duck and wash himself all over; then, returning to land, squeeze the water out of his feathers with his bill, and stand in the sun to dry. But he never seemed to swim for pleasure or to fish, in which respect he differed from the three junior members of his tribe, also locked up in the gardens. Another peculiarity of his was that he would never touch any food but fish. The others soon learned to eat and relish horse-flesh on occasion, but Jack stood out stanchly, and fish, and fish only, he would have, at whatever cost, all attempts at deceiving him being in vain. Jack knew his friends and enemies well, and when he first came, and until the death of his original owner, a Mr. Egan, it was absurd to see the way he attached himself to that gentleman, running to meet him at the gate, and never leaving his side. For some time before his death he subsisted on a stimulating diet of live eels and whiskey-punch.

 

Species of Dicotyledonous Plants.—The number of that great section of flowering plants which, when the seed sprouts, give off two ledons, or embryonal leaves, is shown in the "Prodromus" of De Candolle, recently finished in seventeen volumes, to be very large. Not counting the eminent men that have given earnest work on it as specialists, it has had the conduct of three generations of De Candolles, the grandfather, Augustin, who dying bequeathed it to his son Alphonse, who in like manner left it to his son Casimir. The first and the second wrought together for years, as did also the second and the third. The work describes 5,134 genera and 58,975 species, which is probably not more than one-half the number of species of dicotyledonous plants existing. The principal natural orders described are:

Genera. Species.
Compositæ 911 8,561
Leguminosæ 288 3,853
Rubiaceæ 225 1,888
Euphorbiaceæ 191 8,272
Scrophulariaceæ 176 1,879
Umbelliferæ 160 1,016
Acanthaceæ 154 1,481
Asclepiadaceæ 184 1,013
Labiatæ 122 2,401
Cruciferæ 100 988
Solanaceæ 65 1,725

The most numerous genera are as follows:

Species.
Solanum 915
Euphorbia 751
Senecio 601
Croton 461
Phyllanthus 447
Erica 429
Salvia 410
Peperomia 889
 
The Pneumatic Dispatch.—The following description of the London "Pneumatic Dispatch," for the conveyance of small parcels of goods from place to place, we take from the Times:

"The pneumatic tube extends from the London and Northwestern Railway Station at Euston Square, to the General Post-Office in St. Martin's-le-Grand. The central station is in Holborn, where is also the machinery for effecting the transit of the trains. Here the tube is divided, so that in effect there are two tubes opening into the station, one from Euston to Holborn, and the other from the Post-Office. The length of the tube between Holborn and Euston is exactly a mile and three-quarters. The tube is of a flattened, horseshoe section, 5 feet wide and 4 feet 6 inches high at the centre, having a sectional area of 17 square feet. The straight portions of the line are formed of a continuous cast-iron tube, the curved lengths being constructed in brick-work, with a facing of cement. The gradients are easy; the two chief are 1 in 45 and 1 in 60; the sharpest curve is that near the Holborn station, which is 70 feet radius. The tube between Holborn and the Post-Office is 1,658 yards in length, and is of the same section, and similarly constructed to the first length. Two gradients of 1 in 15 occur on the Post-Office section, but this steep inclination is in no way inimical to the working of the system. The Holborn station is situated at right angles to the line of the tubes, which are therefore turned toward the station into which each opens. All through-trains, therefore, have to reverse there, and this is effected in a simple manner by a self-acting arrangement.

"The wagons, or carriers, as they are termed, weigh 22 cwt., are 10 feet 4 inches in length, and have a transverse contour conforming to that of the tube. They are, however, of a slightly smaller area than the tube itself, the difference—about an inch all round—being occupied by a flange of India-rubber, which causes the carrier to fit the tube exactly, and so to form a piston upon which the air acts. The machinery for propelling the carriers consists of a steam-engine having a pair of 24-inch cylinders with 20-inch stroke. This engine drives a fan 22 feet 6 inches in diameter, and the two are geared together in such a manner that one revolution of the former gives two of latter. The trains are drawn from Euston and the Post-Office by exhaustion, and are propelled to those points by pressure. The working of the fan, however, is not reversed to suit these constantly-varying conditions; it works continuously, the alternate action of pressure and exhaustion being governed by valves."