Atmospheric Pressure in Past Geological Ages THE modern development of aviation suggests the question whether the atmosphere of the earth was denser during the carboniferous epoch than at the present day. This subject is briefly discussed by a writer in Cosmos, whose remarks we reproduce here. "Among the animals which people the earth we find representatives of all sizes, from the microscopically small animalcule to the great elephant. But within the limits of any one species the scale upon which the individuals are built does not differ very materially; we do not, for example, find specimens say ten times larger than their adult congeners. "It is easy to show good mechanical and physical reason why this should be so. Consider two birds, geometrically similar, such as two swallows for example, mid imagine the second to have ten times the normal size. This bird will then have all its linear dimensions ten times as great as the normal bird, while the surfaces will be one hundred times as great. In this way all the cross sections, the thickness of the muscles, especially of the wing (muscles, being increased one hundred fold, we may safely take it that the strength of the bird will also be increased in the same proportion. But on the other hand, it must be remembered that the volume, and hence the weight of the body, will be increased one thousand fold. Thus this large swallow, built on ten times the normal scale, would find itself quite unable to rise into the air or to sustain itself there, for it is relatively ten times less strong than its congeners: with muscles one hundred times as strong as theirs it is called upon to perform one thousand times the work. "As a matter of fact, an examination of the flight of different kinds of birds having approximately the same form shows that flight becomes more and more difficult as the weight increases ; large birds substitute as far as possible sailing flight (which is the characteristic motion of our aeroplanes) for flapping of the wings. Thus the size of animals capable of flight has an upper limit, and this seems to be reached, in the present state of nature, by the large birds, so far as sailing flight is concerned, and by the large insects, so far as flight by wing vibration is concerned. "And yet in past ages much greater animals have flown. One reptile of the group Pterodactyl had a span of over thirty feet, which exceeds that of a racing Blriot; this creature lived during the cretaceous period and flew as far as 90 miles inland. Certain dragon flies of the carboniferous era measured over three feet from tip to tip of their outspread wings. Under present conditions it would be quite impossible for these creatures to fly. The most natural supposition is that in the times when these creatures flew through the air, the atmosphere had a greater density than it has at present. This is the conclusion reached by Mr. Harle. In the estimation of this paleontologist, the existence of these great flying animals during cretaceous and carboniferous times indicates that atmospheric pressure at that time was greater than at present." The Autogenous Cutting Process in Handling Wreckage FOR some time past, the well-known autogenous fusing process (oxy-acetylene blowpipe) has been used with great success for clearing up wreckage after fires, explosions, and similar accidents. An interesting case occurred in a town in Germany, where a school building in the course of construction collapsed, burying a number of workmen under the debris. As good fortune would have it, an oxy-hydro gen cutter happened to be available in the immediate neighborhood, and with its aid the iron parts were cut through in short order, and the workmen were extricated from their hazardous pr'son, The importance of the oxygen blast is, of course, still greater in cases in which the construction is entirely made of iron. Thus, fo'r instance, it was very extensively used in clearing up the wreckage after the collapsing of a large gasometer in Hamburg in December, 1909. The lightning rapidity of the cutting burner is of particularly great utility in the case of railway disasters, where it is essential that the work be performed as quickly as possible so as to clear the road. At the present day, numerous railway corporations have adopted autogenous cutters as a part of the equipment of their wrecking cars. Municipal fire departments also have installed this apparatus. In Germany the process is almost universally carried out with hydrogen and oxygen instead of acetylene and oxygen, because the hydrogen is readily compressible into steel bottles, while acetylene cannot be thus stored without special precautions, since it is liable to explode. The Kodophone IT is very desirable for an aeronaut to know the vertical velocity of his balloon, relatively to the air. Instruments for indicating this relative velocity have been invented by Neumann and by Lentz. The name Kodophone has been given by Lentz to his instrument, which is described as follows in Prometheus: A small windmill is suspended from the balloon, with its plane of rotation horizontal, in the manner indicated in the diagram. The windmill is connected by wires with two electric bells of different pitches and a battery, contained in a case which is attached either to the side of the car or to the suspension ring above the aeronaut's head. The connections are made in such a manner that one bell sounds when the balloon rises, and the other when it sinks, relatively to the air. The velocity of relative' ascent or descent is indicated by the length of the interval between successive strokes of the bell. This The Kodophone. automat c device is especially valuable at night and at any time when the aeronaut's attention is distracted for any reason. A Practical Manufacturer on the Synthesis of Rubber IN the May number of the new journal. KuMststoffe, Dr. Gerlach-Hannover, a practical rubber manufacturer, makes the following statement: "The problem of producing caoutchouc synthetically has been solved. But just as in the case of indigo 20 years elapsed before the synthetic product was successfully launched, it will take at least 20 years before synthetic rubber will make its appearance commercially. It will take perhaps longer with caoutchouc because the physical properties of this material are not as well known as those of indigo. The high price of the natural product stimulated research and, after the pioneering experiments of Harries, the Elberfeld Farbenfabriken have finally succeeded in producing larger quantities of a product derived from a material closely related to isopren. At this stage of the development it was found out that there exist many sorts of rubber which are near relatives, but still possess different characteristics. "The first synthetic caoutchouc which was placed at my disposal, for example, did not unite with sulphur and had a leathery appearance. This was not to be wondered at, as there are known some varieties of natural caoutchouc which cannot be vulcanized. Soon another sort of rubber came to my notice which showed better affinity for sulphur, but still could not be perfectly vulcanized. Above all it lacked elasticity. Soon, however, larger quantities of a third sort were submitted to me which to my great astonishment showed all the excellent properties of natural rubber. "But now the question arises whether this material of the Elberfelder can be economically produced on a large scale and may thus become a danger for natural rubber. It cannot be denied that the substance, which possesses good qualities, can be utilized for practical purposes, Its price is not high but it is a complex question to decide whether this synthetical product will become a danger to natural rubber. All kinds of economical and commercial conditions must be taken into consideration. One thing, however, is certain, that synthetic rubber will soon be a commercial article." Highway Engineering as a Profession ACCORDING to Prof. Arthur H. Blanchard, who recently lectured before the Society for the Promotion of Engineering Education, the technical graduate who is attracted to highway engineering has several more or less well-defined fields open to him. These are: "The highway departments of municipalities and towns; those of States, counties and parks; the engineering organizations of contractors; and the engineering and sales departments of companies dealing in materials and machinery used in highway work. In city and town work matters relative to the construction and maintenance of streets and pavements compose the bulk of the work assigned to the highway departments, together with more or less road engineering problems. .With State, county and park departments, the construction and maintenance of all types of road surfaces and bituminous pavements constitutes 90 per cent of the work of such organizations, while certain problems in street pavements and highway bridges have to be dealt with occasionally. The prevailing idea, however, that the two fields just mentioned are easily separable, and that the preparation for one should not be the preparation for the other, is essentially wrong. Since the lines of demarkation between the above fields are rapidly becoming obliterated, the successful highway engineer of to-day, whether engaged by the city or State, must have a comprehensive knowledge of all branches of highway engineering and allied subjects. Otherwise it is obvious that it will be impossible to follow that important principle of economics of highway engineering, the adaptation of methods and materials to' local conditions. "In contemplation of these opportunities, the essential prequisites of a successful career as a highway engineer must be given due consideration in order that the future prospects offered by this field of engineering may be thoroughly understood." Prof. Blanchard recommends four years' training in a course in civil engineering, practical experience in both field and office in connection with the construction and maintenance of roads and pavements on a system of highways, and the acquisition of knowledge along certain lines of particular value to the highway engineer, by which last is meant knowledge of the economics of highway engineering, materials of highway engineering, management engineering, highway laws and systems of administration, mechanical appliances used in highway engineering, highway bridges and culverts, road and street surveying, drafting and designing, methods used in road material laboratories, advanced dynamic and structural geology, lithology, petrology and petrography, processes of industrial chemistry, methods of testing bituminous materials and the interpretation of results, and finally advanced highway engineering covering the most recent practice throughout the, world in the construction and maintenance of all kinds of roads and pavements. The problem before the educational institutions of this country is that of determining by what method the subjects outlined above can be offered upon a practical basis, Prof. Blanchard does not favor a four years' undergraduate course in highway engineering, partly because undergraduate students are not sufficiently mature to acquire the benefits which should be derived from a combination of practical experience and specialized knowledge. The most practicable plan is to arrange a definite course of instruction as a unified graduate course based on the assumption that the technical graduates enrolled for the master's degree will hold undergrad uate degrees in civil engineering. If the graduate instruction is to be given in the period from about December 1st to about April 1st, it will be possible for practising highway engineers, especially first, second, and third-year graduates, to use the winter period advantageously in acquiring advanced knowledge under favorable circumstances. Columbia University will offer a course next year which will cover the field of subjects referred to in Prof. Blanchard paper, and will, in amount, be sufficient to satisfy the requirements for the masters degree.
This article was originally published with the title "Abstracts from Current Periodicals" in Scientific American 105, 15, 319 (October 1911)