Page:The Building News and Engineering Journal, Volume 22, 1872.djvu/273

 Marci 29, 1872. THE BUILDING NEWS. eee SS — eee finite variety of sky-line, for which they always afford opportunities. A late President of the Insti- tute of Architects, and distinguished architectural student—Mr. Beresford-Hope—has often and at much length descanted on this subject; and it is sufficient for our purpose to point out how very much such an outline as that of the Houses of Parliament effects for the general aspect of London, when com- pared with our other public buildings in the Classic or Renaissance style, such, e. g., as the Post Office, the British Museum, the National Gallery, or Somer- set House, whose only effect is one to be seen from the very streets themselves in which they are erected. After the Houses of Parliament, the next great opportunity of a public building was the proposal to erect the Foreign and War Offices. Lord Palmer- ston’s ignorant prejudice against all Gothic buildings —indulged the more vehemently, because at the mo- ment all substantial power in matters of State was slipping out of his hands—prevented the carrying out of Mr. Scott’s design for this building. This was a very real subject of complaint and regret, in spite of the fecling entertained by some that the de- sign was conceived to some extent upon the principles which Barry had adopted in the Houses of Parlia- ment, though wrought out with Mr. Scott’s usual fertility of invention and taste. The Courts of Justice are the third great oppor- tunity, and we rejoice that all the competing archi- tects gave in their adhesion to Gothic as the only practical style in making their designs, and that the opportunity is afforded of acting in the construction of the building on the principles on which alone, as we have shown, all good Gothic buildings in all times have been designed. The component parts of such a building are not very many, but they are diverse. There is of necessity a collection of Courts of Justice round a Central Hall; there is of neces- sity a vast number of rooms of varying importance for Judges, officers of the courts, and mere clerks. Finally, there is a broad distinction between Courts properly so called, and their belongings, and the legal offices. If the principles which we have attempted to. lay down have any truth whatever, then un- doubtedly all these varying rooms and chambers ought, as far as possible, to be distinctly and intel- ligibly treated and differencedin the actual building. And it is, as we believe, because this has been at- tempted in the design, because in so doing popular traditions and modern customs have been rudely op- posed, that the architect and his design have been so heartily attacked by some of his brother archi- tects. BS ig GRADIENTER SURVEYING.* Ae experimental survey has just been completed for the extension of the Shenandoah Valley Railroad, from Covington, Va., to Russelville, Ten- nessee, the results of which, as regards economy and rate of progress, are so extraordinary that a brief account of the system which has been adopted may not prove uninteresting. The number of miles surveyed was 300; the whole time in the field about 5 months; the whole cost of the suryey, 1,850 dols., of which, 1,050 dols. was for salary of the assistant’ in charge, leaving only 800 ols. to cover expenses of waggon and party, including supplies and outfit. A considerable portion of the route was through brush and laurel thickets, where roads were cut for the ox waggon which carried supplies. The average daily progress was three miles, maxi- mum 73 miles; but on long summer days 10 miles in open ground would be practicable. The instrument used was Wiirdemann’s gradi- enter, to which stadia wires for reading distances by means of rods had been added. DESCRIPTION OF GRADIENTER. The gradienter consists of a light but very power- ful telescope, with attached spirit level and compass box, horizontal limb graduated from zero to 360 deg., circular spirit level attached to limb, and in- stead of vertical limb, a peculiar arrangement for measuring angles of elevation, called a percentage screw. This is the ordinary form of the gradienter as manufactured for the Coast Survey Department, but to adapt it to railroad experimental surveys, three stadia wires were added, the middle horizontal wire intersecting the vertical wire in the axis of the telescope, the other two forming spaces having the relative proportion of 1, 2, and 3. The percentage screw is the great feature of this instrument. It is finely and accurately cut, and carries a horizontal disc of about 14in. in diameter, on the periphery of which are 100 subdivisions. This dise revolves in contact with a vertical gradu- ated scale, and the parts are so calculated and ad- justed that one complete revolution of the percent- age screw corresponds with one division of the scale, and each division marks 1ft. in 100 of elevation or depression; the percentage screw subdivided this foot into 100 parts with surprising aecuracy, show- ing great nicety of mechanical construction. In testing the instrument at a distance of 500ft., the elevations, as determined by the percentage screw, would seldom vary more than an inch from true levels; and although this would not be sufficiently accurate for canal surveys or railroad final locations, yet for experimental lines such an instrument is of great utility, and it can be used as an ordinary level with less rapid progress where great accuracy is required. RODS. The rods used were of peculiar form, constructed by the writer to facilitate the reading by the assistant of levels and distances at the same time. Each rod consisted of two pieces 3in. wide, tin. thick, and 10ft. long, connected by hinges so as to shut together like the leaves of a book, and thus protect the grad- uation from abrasion. One side of these rods was graduated in feet, tenths and hundredths from the bottom up, and read as an ordinary levelling rod by the assistant. The other side was graduated from the top down for distances, by first measuring accurately 500ft., and marking the space covered by the ex- treme wires. This space being subdivided into 5 parts, each part would represent a distance of 100ft., and each of these spaces was again subdivided into 100 parts representing feet. The graduation was peculiar and very legible. MODE OF USING THE GRADIENTER AND RODS. The adjustments of the instrument are simple, but as the threads.of some of the most important screws are fine and delicate, care must be taken not to strain them. The instrument being adjusted, the first operation consists in levelling by the sensitive circular level attached to the horizontal plate. Next, to bring the zero of the percentage screw in contact with the zero of the scale, when the level attached to the tele- scope should also be horizontal. If it is not, the in- strument is out of adjustment. Next, place the zeros of the vernier and limb in juxtaposition and clamp them. Next, turn the object end of the tele- scope towards the north and unscrew the needle; when the needle has settled, bring the zero of the compass are to it by means of the tangent screw, and clamp firmly. The telescope is now in the direction of the meridian, and the verniers at zero ; the needle may now be screwed up; it is not used for reading courses, but only to determine the meri- dian, for which purpose it is made long and sensitive. The vernier is now unclamped and the courses read from 0 deg. to 360 deg. The observer now turns the telescope to the back rod, and, bringing the top hair to the top of the rod by means of the percentage screw, reads and records the distance and the course. Next bring the zero of the percentage screw to the zero of the scale. If the rod can be seen, the level can be read at once; if not, the telescope must be eleyated or depressed, so as to bring the middle wire against the rod. It is most convenient in practice to turn the percentage screw a given num- ber of complete revolutions, as it renders calculation more simple. A single example will be suflicient for explanation. Suppose the distance as recorded is 480ft., that the level from the observer strikes below the bottom of the rod, and that the telescope has been elevated 5 turns of the percentage screw to bring the rod into view; as each turn corresponds to Ift., in 190, 5 turns would be 5ft., and in a distance of 480ft. the elevation of the line of sight would be 480 X 5 =24ft. above the level. If this line should strike the red at a reading of 5:42, then 24—5:42—18°58, which would represent the level of the instrument below the bottom of the rod, and the reading would be entered in the column of back sights 18-58. Suppose the ground continued to descend, and the forward sight should read 30°20, the difference of level between the two stations, equal to the difference between the back and forward sights, would be 30-20—(—18-58) = 48-78ft. It will be perceived that by this system negative rods can beread, which is not possible by the ordinary system of levelling, where, if the line of sight strikes below the rod, the instrument must be moved to a higher level. It is also possible, by means of the percentage screw, to read positive rods of 40 or 50ft. with considerable accuracy, and thus avoid the short intermediate stations required in ordinary levelling. The survey of the Shenandoah Valley extension, just completed by O. Barrett, Jr., is the first upon which this system of surveying has been used. The results, however, are very satisfactory. The cost per mile as compared with former surveys has not been more than one-fourth, and the daily progress double. The engineer records at each setting of the instrument courses, distances, total distance, back sight, forward sight, total level, and slopes. It is not absolutely necessary that a man in his party should be able to read or write, but it is convenient to have an axe man who can mark stations. One axe man and two rod men constitute the party. Each of the rod men should earry a short bill hook suspended from his belt to be used in cutting through thickets. One rod could be dispensed with, but the progress in open ground is much more rapid with two. Instead of using stakes exclusively, it is prefer- able, where practicable, to mark stations on trees, fences, rocks, and buildings, and to mark with paint. The measurement of distances by the stadia wires is, on broken ground, quite as accurate as ordinary chaining. And in crossing streams, marshes, or other obstructions, it has great advantages; they scarcely retard progress, where measurement by chain would be impracticable. —————— ened OUR WATER SUPPLY CONSIDERED IN RELATION TO PROTECTION FROM FIRE.* PE Oeree and reasonably so, at the re- ception afforded by the Court of Common Council to his recent motion to consider the desira- bility of providing an additional water supply for the City for the better protection of life and property from fire, Mr. Henry A. Isaacs has embodied the principles of his plan, and the facts on which he bases his arguments for its adoption, in this pamphlet. He points out that the East London Water Com- pany, which has hitherto derived its supply from the River Lea, is now constructing new supplemental works at Sunbury-on-Thames; and that the inhabi- tants of that locality are already complaining that the water companies take so much from the river as to leave it dry in many parts (to the serious detri- ment of the health of the district); that the new river company’s supply has decreased half a million gallons per annum since 1856; and even in the absence of any very extensive conflagration, and especially in the summer season, the consumption of water reaches the maximum of the companies’ sup- plies, and the demand is very frequently in excess of the said maximum; and that in 1871 there was a dearth of water in sixty-seven cases of fire. These facts Mr. Isaacs considers amply justify his anxiety for the utilisation of another source of supply prac- tically inexhaustible, and, according to him, avail- able at a comparatively small cost. He suggests: The erection of two pumping stations or towers (each having a reservoir at its summit), one on the north, the other on the south, of the Thames, and as near to London Bridge as may be found practicable. The laying down mains con- nected with the pumping stations aforesaid, for an independent water supply for the extinction of fires, and for cleansing the streets, and flushing the sewers within the City. The water to be derived from the Thames by means of pumping engines of sufficient power to deliver it at an altitude above that of the highest house or warehouse in the City. The erec- tion of hydrants, to be attached to the aforesaid mains, the street lamps to indicate the points where- at the fire hose and keys of the hydrants would be attainable. The advantages of such a system he thus summa- rises: In the event of an outbreak of fire, the neces- sity for sending for the fire brigade in one direction, and for the turncock in another, the loss of time be~ tween their being summoned and their arrival, the intervention of the fire-engine, the turning on one service and shutting off another, and the inevitable doubt as to a sufficient supply, would be entirely obviated. Two or three practical men have estimated the cost of the scheme at from £100,000 to £120,000. One gentleman, to whose judgment, knowledge, and experience, Mr. Isaacs seems rather more disposed to trust, has estimated it at £150,000. This sum raised —as it might be upon the security of the consolidated rate—at 4 per cent., would cost £6,000 per annum ; to which add, say, £2,000 for working expenses, and we have a total cost of £8,000 a year. To have a good margin, Mr. Isaacs adds one-third to the esti- mated cost of the works, and calls it £200,000, which will make the total £10,000 per annum. This sum, large as it is, would be covered by the addition of one penny in the pound to the consolidated rate. sidered in Relation to the Protection of the City of London from Fire.’ By H. A. Isaacs. London: Collingridge.
 * By H. Haupt, C.E., in Van Nostrand’s Magazine.
 * “Our Water Supply (Present and Prospective) Con-