Page:The Building News and Engineering Journal, Volume 22, 1872.djvu/197

 / Marcu 1, 1872. THE BUILDING NEWS. 181 that there were descriptions of rock in which the first. sort was more suitable, while at the same time there were cases in which the second class could be more advantageously employed. ach class of machines might, again, be subdivided, one set of machines acting on the rock by means of blows, and the other by means of a steady grinding or rubbing process. Amongst the machines of the first class, or those which broke away the whole rock by mechanical force, might be mentioned the machines of Captain Penrhys and Mr, Brunton. The first of these consisted of a large gun metal dise nearly the full size of the heading to be driven, mounted on a frame something like a gigantic buffer. The face of this dise carried a large number of steel cutters, and the dise was moved bodily backwards and forwards by means of a compressed air engine. It was driven against the face of the rock with such force that the cutters dug into the surface, and, by a continual repetition of this pro- cess, the whole face was gradually broken away, and the machine moved steadily forward. In Mr. Brunton’s machine, on the other hand, there was an entire absence of all shock. On the face of the machine were several cutters closely resembling quoits. The number might be 6 or 12. These cutters were held against the face at one edge; the machinery moved them round, giving them rather a rolling than a cutting motion, so that the cuts somewhat corresponded to the ruts caused by a wheel in soft roads, except that, instead of being at right angles to the surface, they were only slightly inclined to it. When these cuts or ruts became two or three inches deep, the pieces of stone broke off, and fell to the bottom of the heading, whence they were carried by a band to the back of the machine, and there tipped into waggons. These pieces of stone were constantly breaking off, and the cutters were gradually passed over the whole surface, so that the entire face was cut away in layers of one or more inches, according to the nature of the rock, The second class of machines comprised those which bored holes in the rock with a view to its being ultimately blown down by an explosive compound. This class might, like the last, be subdivided into two divisions, the first comprising those machines which effected the drilling by means of a succession of blows; and the second comprising those which effected their purpose by a regular motion. The machine latterly used in the construction of the Mont Cenis Tunnel was a characteristic specimen of the first class. In this machine the tools were driven by compressed air, and drilled holes in even the hardest quartz with astonishing rapidity. Another machine of the same character was that patented by Mr. Doering. It consisted simply of one drill driven by compressed air. It was simply a mechanical miner. It was worked at the rate of 200 er more blows per minute, and, as each of them was given with considerable force, it worked at a great speed, boring a hole into hard limestone at the rate of 1}in. per minute. Its great advantage was that rt was very small and portable, and would drill a hole in any direction, which made it particularly useful for odd jobs; while machines of more am- bitious design, like that used for the Mont Cenis Tunnel, could be used with economy only in cases where a long heading had to be run. The first specimen of the second division of machines which was actually employed, was, Mr. Morrison believed, a machine for slate quarrying. In this machine a hollow steel tube was turned round continuously and pressed against the slate. Itwas suppliedin some cases with water and sand, and with great expedition it eut a circular hole into the slate, the core which was left being easily detached after the tube was with- drawn. The slate was then broken up either by powder or by wedges, according to circumstances. This machine had, not, however, been much used, except for slate quarrying; but there was another machine of similar design which was now coming largely into use. By it the hole was cut in the same manner—t.e., by a tube, the core being afterwards withdrawn, but instead of merely metal tubes being employed the ends of the tubes in this machine haye diamonds set in them. In another boring machine of great ingenuity, a stream of quartz sand was driven against the face of the rock by a jet of steam, and it was stated that the power of this stream of sand was so great that holes were drilled by it more quickly and easily than by any other process. As to the relative merit of these machines, Mr. Morri- son said he had come to the conclusion that the first- mentioned class, or those which entirely broke up the rock by mechanical means, were the most suitable for the softer classes of rocks, such as chalk, slate, and sandstones of various descriptions, while those which drilled holes for blasting could be used most effectively in hard rocks, such as the very hard de- various igneous rocks. In each of the classes, again, he considered that those which effected their purpose by steady grinding could best be employed in tun- nelling rock of uniform hardness and moderately free from cracks—i.e., for machines of the first class chalk, slate, and compact sandstones, and for those of the second-class compact limestones, traps, &e. ; while rocks of irregular character, such as conglomerates, or granite with large erystals of quartz, were best attacked by those machines, whether of the first or second class, which effected the operation by blows instead of by steady cutting or grinding. With regard to permanent way, Mr. Morrison remarked that fish-bellied rails, stone sleepers, and many of the other inventions of former times had long been out of date, but changes of great im- portance were still being made in our permanent way. In this country very few iron sleepers were used, all the lines being laid on timber sleepers, either cross or longitudinal. At one time all the broad gauge lines had longitudinal sleepers, and toa great extent this was still the case; but on many of the new lines, and in relaying the old lines, cross sleepers were coming into fashion on the broad gauge lines, though the broad gauge itself would soon be a thing of the past. But while there was a great con- cord of opinion as to sleepers, there was by no means the same uniformity in practice as to rails, The larger railway companies, where there was a great deal of traffic, used the double-headed rail, with cast-iron chairs, but on all branch lines the Vignolles or flat-bottomed rail wasin favour. This latter rail made a very fair road, and it was, Mr. Morrison believed, impossible for any chair road to equal it at the price; but where first cost was not an all im- portant consideration, there could be no doubt that the chair road was vastly superior to that formed with flat-bottomed rails. On the subject of curves and gradients the author alluded to a modern peculiarity which he regarded as anything but animproyement. In earlier days lines used to be laid out with curves of 30 or 40 chains radius, and with comparatively flat gradients through difficult country. Nowadays railways went dodging up and down hill and round curves that might almost be called corners. Now where this was done for the purpose of saving first cost it was often a most judicious course of proceeding, and no engineer would be doing his duty who did not open his eyes to the fact that such curves and gradients were practicable, and who did not use them when neces- sity required. But of late years an idea seemed to have gained ground that because quick curves and steep gradients were not impracticable they were therefore not objectionable. No idea could be more mischievous. In every case the flattest curve and gradient possible should be adopted, and an engineer was not doing his duty to his employers if he did not in every case do his utmost to lay out the best line the nature of the country would admit of, instead of contenting himself with choosing a line which should have no curve or gradient beyond some arbitrary limit which had been fixed on beforehand. es THE ELEMENTS OF PLANE AND SOLID GEOMETRY.* ee is admitted by nearly all who have given careful attention to the subject, that the book we call “Tuclid” is not altogether worthy of the place it has so long occupied as a text-book of geometry. As yetno work has appeared which can be accepted as a suitable text-book, though several useful treatises on elementary geometry have been lately published. The work now before us is one of these. It is a work which the student of geometry may read with interest and profit. We cannot say, how- ever, that it is well suited for the beginner. It is, indeed, in some respects, less inviting even than Euclid; and is not characterised by the clearness of expression, compactness and neatness of arrange- ment, and suggestiveness of tone, which a text-book of geometry requires in an especial degree. It appears to us thatin a first book of geometry, those difficulties which have so long been recognised in the formation of definitions and axioms should not be suffered to obtrude themselves before the notice of the young learner. We must not frighten the beginner by being too logical. For example, the definition of a straight line as ‘one which lies evenly between its extreme points” is not logically exact. But it is better in a book for beginners than Mr. Watson’s definition: ‘A straight line is a line of such a form that if any portion of it be applied to any other portion, so that the extremities of the one portion coincide with those of the other, then scriptions of sandstone, limestone, quartz, and the | H. W. WArson, M.A. London: Longmans & Co, every intermediate point of one portion must coin- cide with some intermediate portion of the other.” Or if such rigidly exact definitions be adopted out of compliment to continental geometricians, then such an inexact definition as the following must be ob- jected to:— Straight lines are added together by placing them one after another in succession in the same straight line, so that one extremity (which ?) of each newly added line coincides with one ex- tremity (which, again ?) of the last added line.” We believe, however, that for beginners definitions should be avoided altogether in favour of described pictures. In like manner, the enunciations of propositions, if employed at all, should be as simple as possible. We believe that they add enormously to the difficulties of beginners ; but if we must have them, they should be clear. The learner naturally supposes he is to master the meaning of the enunciation before proceeding to the illustrated description; and he is apt to find more trouble by far with the enunciation than with the reasoning by whick it is established. For instance, it seems too severe a tax on the powers of a beginner to submit such an enunciation as the following (prop. 27 of Mr. Watson’s first book) to his consideration :— The locus of a point from which the sum of the per- pendicular distances upon two given intersecting straight lines is equal to a given finite straight line, is the base, of that isoceles triangle formed by the given lines, such that the perpendicular dis- tance of either of the angles at the base from the oppo- site side is equal to the given finite straight line. We select this instance because, apart from the general objection against enunciations of this sort, there is a special objection against this proposition, as an alto— gether useless onein its present form. Tell the student this, that if he takes a point in the base of ar isosceles triangle, and lets fall perpendiculars on the sides, the sum of those perpendiculars will be the same wherever the point may be taken, and you have told him, we conceive, a very useful geometrical fact; but if you make the above quoted statement about a locus, &e., you succeed only in bewildering him. As respects arrangement, we haye some sugges- tions to offer. The volume is divided into books the beginning and end of which can only be found from the index ; it would be an improvement, if in future editions, the headings of the pages indicated the number of the book. Each book is divided int sections, in which are propositions, definitions, notes, examples, and general explanations, scattered seemingly ad libitum. It would be easy to substi- tute a more orderly arrangement. In passing, we may notice that in the preface there is a reference to “the note to proposition 6, book 5, p. 153,” but that no such note appears in the text. The student who has already mastered Euclid, so far as it is read at the Universities, will find some parts of this work very instructive and interesting, more especially if his reading has not brought him into contact with the continental text-books of geometry. ge ROYAL INSTITUTE OF BRITISH ARCHITECTS. SPECIAL general meeting, of members only, will be held on Monday next, March 4, to consider the recommendation of the Council with respect to the award of the Royal Gold Medal, the Soane Medallion and other Medals and Prizes of the Institute for the year 1871-72, viz. :— That the Royal Gold Medal be awarded. subject to her Majesty’s gracious sanction, to Herr Ober- Baurath Professor Freidrich Schmidt, Hon. and Corr. Member, President of the Austrian Institute of Engineers, and Architect to the Cathedral of St. Stephen, Vienna. That the Soane Medallion (with the sum of £50, under the usual conditions) be awarded to the author of the drawings distinguished by the motto of “ Steadfast.”—(Subject of design—A Town Hall in a Country Town.) That the Institute Silver Medal, with £5 5s., be awarded to the author of the drawings distin-~ guished by the motto “ Forte secutum salus ducum.” (Building illustrated—Tattersall Castle, Lincoln- shire.) That in the same competition a Medal of Merit be awarded to the author of the drawings bearing the motto of “ Alta Troll.” (Building illustrated— All Saints’ Church, Edington, Wiltshire.) That in the same competition, the two sets of drawings bearing the respective mottoes of ‘ Espe- rance” (Building illustrated—S. Leonard’s Priory, Stamford), and “Insta” (Building illustrated— Publow Chureh, Semersetshire), be distinguished by Honourable Mention,
 * “The Elements of Plane and Solid Geometry,” By