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ent parts of the line, so as to facilitate choose some well-marked point, set the the forwarding of supplies, and, in short, cross hairs upon it a little before dark, acquire the greatest amount of knowl- and see that no one disturbs the transit edge of the country in the least possible between that time and the time when time. Upon his report depends the the observation is to be taken, the hour
for which can be found in the Nautical PRELIMINARY SURVEY,
Almanac. It is usual to observe the star the party for which should consist of a when at its greatest eastern or western chief, a' transitman, two levelers, two elongation, but it can be observed when rodmen, a topographer, one or two pick at its maximum depression below or eleetmen, two chainmen, five axemen for vation above the pole, when the instruthe line, and one for each leveling party, ment is provided with a tangent screw three to six or even eight packmen, and to produce a slow motion in a vertical sometimes a commissariat officer and an plane. In the latter case no correction is explorer.
required, so when the star has reached As in most preliminary surveys, the its greatest elevation or depression, duties of any one of these officers are which can be ascertained by keeping the substantially the same. The instructions intersection of the cross hairs on the star, of the chief engineer of the Canadian being careful never to pass it, and noting Pacific Railway to the Staff may be when it appears to cease rising or falling, taken as a general illustration of their all that is necessary is to take the readcharacter. The gentleman placed at the ing of the horizontal circle, which will head of a party is required to take gen- give the angle that the line from the eral charge of it, and is held responsible terminus to the point chosen makes with for the execution of all instructions, as the true north. "In observing the greatwell as for the maintenance of proper est elongation, keep the vertical hair on discipline in the party. Every member the star and note when it appears to of the party is under his charge and must cease changing its azimuth, then take obey his orders. In conducting the sur- the reading, which will be the angle that vey, he is expected to be at its head the above-mentioned line makes with the every day, exploring in front and to the vertical plane through the star at its right and left of the line, in order to see greatest elongation. The correction for what obstacles may be in the way of the this angle can be found by a very simple same, and, if serious, decide as to the rule given in the Nautical Almanac, ard best manner of avoiding them. When is to be added, if the star lie between the he finds it necessary to leave the party, pole and the line, and to be substracted or in the event of illness, he should nom- if it does not. Should the line lie beinate the person to act in his place for tween the pole and the star, this will the time being; in the event of his fail- give a negative result, which shows that ing to do so the transitman should take the angle so obtained is to be laid off charge.
from the pole towards the star; i. e., if The duty of the transitman is to run the elogation be east, the bearing given the instrument, keep the notes, and in hy the minus angle will be east. It is case there is no topographer, to take the easily seen that the latter method is by topography.
far the better, for it is necessary to use The duty of the first leveler is to only the horizontal ta nt screw (the make a profile of the line and cross sec- one which gives the upper motion, of tions; that of the second leveler is to course), while in the former both the check the bench marks and to assist in horizontal and vertical screws have to cross-sectioning.
be turned at the same time. Having The principal duty of the others of the found, then, the true bearing of a fixed party is to obey all orders with diligence line, the true bearing of the initial line and to the best of their ability.
of the survey can be easily ascertained Before starting the survey the transit by measuring the horizontal angle beshould be set up over the terminus and a tween the two lines. true north and south line determined by Suppose the party all ready to start means of an observation of the pole star. and the initial bearing taken. The axeTo do this, place the instrument at zero, | men go ahead clearing the line and the
chainmen follow, driving stakes about nearly over the nail by driving down first three feet long and two inches wide one leg and then another, then moving firmly at every hundred feet, numbering the feet of the tripod until the point of them consecutively, with red chalk as the plumb.bob exactly covers the nail. If they go. When it is necessary to change the instrument having a shifting head the instrument, either on account of the much time and trouble will be saved. distance of the picketman, who has been Hubs should be placed at the summits keeping the axemen on line, a sudden and bases of hills, so as to avoid as much rise or fall of the ground or a desired chopping and moving of the instrument change of direction, the transitman gives as possible. At intersection points the the signal previously agreed upon for hub-stakes should be marked "apex, “hub,” the picketman chooses a conve- and the angle to right or left should be nient spot for setting up and finds written on another of the squared faces. “point” on the line into which one or The best kind of a hub is the stump of two of the axemen drive a stake from a tree that comes directly on line, for it four to six inches in diameter, and from cannot be knocked out of place. In runone to six feet long according to the ning through comparatively level country quality of the ground, and the picket-it is well to keep as much as possible to man finds "point on hub” into which he the low ground without lengthening the drives a nail.
line greatly or making it too crooked. The transitman then sets the back It is to be remembered that the survey picket, which in bush work is a small is not a final one, so that it does not pay straight sapling whitened on one side, to turn out for a small ridge, but to go with a cross-piece eight or ten inches over it and take a cross section on the long, held in a cleft near the top, picks summit to where it tails off. In case of up his instrument, moves on to the new trying to reach a summit, it is necessary hub, over which he sets up, sights to his to follow the contours of the hills so as back picket, reverses his instrument and to obtain a gradual rise. In hilly counstarts the axemen and chainmen to work. try where the line rises and falls in long Before giving hub again, the transitman stretches, the best way to proceed is to should sight once more to the back pickel follow up a stream to near its source, in order to satisfy himself that his instru- then cut across the divide and follow ment has not been moved, and if uncer- down another stream on the other slope. tain of the adjustment should turn the If the banks of a river are high, a good instrument round 180° by means of the crossing can often be found by going up lower movement, sight to the back stream, where they are usually lower. In picket, reverse and give “second point crossing a lake on the ice soundings on hub." If this coincides with the first should be taken, as it might be found one all right, if not, then the distance desirable to drain the lake. between the two (measured, of course, Offsets usually are taken at right at right angles to the line) must be bi- angles to the line, but sometimes inclined. sected accurately and the nail be driven Short ones can quickly be turned off by at the point of bisection. This is, in standing on the centre line, stretching fact, performing the second adjustment the arms at full length along the line, of the transit. Beside each hub, at a then bringing them suddenly together; distance of about three feet, should be with a little practice a right angle can driven a large stake called "hub stake," thus be turned quite accurately. For five feet long, at least five inches in diame- long distances it is necessary to use an ter and squared at the top. On it should instrument of some sort, a cross head be written the exact chainage of the being as good as any. Offsets are needed point on hub, and the distinguishing to locate the baser of hills and the edges mark of the survey party, which is usu- of streams. Traverses of ridges or rivers ally one or two letters. In setting up in are most easily made with the compass, swampy ground, "legs ” or long heavy provided there is no local attraction, by stakes should be driven flush with the setting up at every alternate station and surface of the ground, in order to pro- reading the bearing of both lines intervide a tolerably firm “set up” for the secting at that point. The compass is nstrument. The plumb bob is brought sometimes used on the main line in level
country where there is no great local at- has a ball and socket joint, by means of traction. Very often there is no instru- which it can be set up in places where it ment used at all, except at the angles, would be impossible to use an ordinary the long tangents being run in by pickets. Y level. The telescope being an invertIt is surprising with what accuracy work ing one may cause a little trouble at first, can be done by the compass and pickets but it does not take long to become acin a comparatively level country.' Run- customed to that. The best kind of ning a picket line in the bush is quite a rod is a piece of well-seasoned pine wood different affair from what is taught at sixteen or eighteen feet long, four inches the R. P. I. during the chain survey, it wide and one and a half inches thick at may therefore be well to describe the bottom, three inches wide, and threeoperation: The pickets are thin straight quarters of an inch thick at top, and saplings, about five and a half feet in divided into tenths and half-tenths. The length, brought to a long fine point at form of level book should be that shown the top, and sharpened at the lower ends in the figure below: for pushing into the ground. The tops of two of them are set on line by the in- Sta. B.S. Int. F.S. H.I. Elev. Remarks. strument about fifty feet apart; a third is then set about fifty feet fart her on, the top being brought exactly on line with the others. A check on the work can always be obtained by glancing back along the line and ascertaining if the last three or four pickets are in one straight line. A pair of field glasses is of great assistance in picketing. To “tie on” to an old line, set a hub on each side of it, The F. S. column is for turning points drive a nail in each along the line of alone, so that by adding up the B. S. and sight of the instrument, and stretch a F. S. columns, subtracting one from the string tightly between the nails. Next other, and comparing the remainder with take
up the instrument, set it up on the the difference in elevation of the starting old line, and in its direction, and sight and final points, a check on the accuracy to a picket moved along the string until of the book can be obtained. Bench covered by the vertical hair; then drive marks should be made about every fifa hub and set a nail at the point thus teen hundred feet, and should be well found.
defined so as to catch the eye readily. After the transit party has made a The ordinary method of making them is good start, the levelers commence work; to blaze the side of a tree or stump, drive they should never approach the transit a nail into a projecting knob on the root closely enough to disturb the back picket. and write the elevation of the top of the If the second leveler finds a difference nail on the blazed part, together with of more than one-tenth of a foot be- the distinguishing mark of the survey tween benches, the levels should be re- party. The exact location of the bench checked. The speaking rod is almost should be noted in the level book in the exclusively used in bush work; it is much column for remarks. To make a good better than the target rod for rapidity, bench mark without the use of a nail, and the leveler is not at the mercy of slice off the side of a stump to very near his rodman, who may often be too ignor- the bottom, and bring the remaining part ant to read the rod. Care should be to a rounded apex. taken to equalize back sights and fore The leveler should note every stream sights, and neither should exceed for and river crossed, its size, direction, level accurate work four hundred feet. It is of surface, difference of levels between possible to read an ordinary rod on a high and low water, velocity of current, clear day at eight or nine hundred feet, probable discharge, and any peculiarities but one cannot rely on levels so taken. which it may seem to possess. While in The best kind of level for rapid work, as the field it is not necessary to work out far as my experience goes, is the Pasto- the elevations of intermediates; it is sufrelli. It is fourteen inches in length and ficient to know the height of instrument
and the elevations of bench marks. should be made every night and the latiEvery evening the leveler should “make tude and departure worked out. Checks up ” his book and plot the profile. Lev- on the work should be made as often as eling can be done very rapidly in win- possible. The check for deflections is ter, as traveling on snow shoes is so made by taking an observation of the much easier than ordinary walking in pole star every ten or fifteen miles and the bush. The uncertainty as to the comparing the reckoned true bearing shape of the ground beneath the snow with the observed, after making the makes it sometimes difficult to get a proper correction for conveyance. This good set-up, but if the three legs of the is found as follows: Let n= the numtripod be kept vertical and the snow be ber of miles in a degree of longitude, a packed well about them, the instrument quantity depending upon the latitude of will be kept as steady as in any ordinary the place, then will 60-n=the correcset-up. If the rodman carry a three- tion in minutes per mile of longitude. foot stake to be pushed through the Calling m the number of miles of longisnow to the ground at intermediates, and tude between the two points considered, upon which the rod is placed, much time 60m:n will be the required correction. may be saved. In this case care should A check for the distance can be roughly be iaken to add three feet each time to obtained by ascertaining the latitude and the reading of the rod. The transit longitude of various points along the book ordinarily used has one page ruled line, by observations of the stars. Checks into squares, each side representing one can sometimes be obtained by tying on hundred feet, and the other page ruled to old lines. If an error be found in the for remarks, a red line running through direction of the line, it may have been the center of each. In case there be a made by recording an angle to the wrong topographer in the party, the transitman side; to ascertain if such be the case, need make note only of the chainage, divide the error by two and see if there magnetic bearings and deflection angles, be an angle on the plot which is equal or being sure to state whether they are to very nearly equal to this result.
If right or left. But if there be no topog. there be one the chances are that the rapher, it will be necessary for him to mistake was made in that way. keep full topographical notes. These the error cannot be located, it will be consist of offsets to right and left wher- necessary to go over the work again, ever necessary, contours of hills, courses commencing at the point where the next of streams, observations as to the quality to last observation was taken. Errors of timber and soil, location of ridges are sometimes made in reading a deflecand lakes, etc., etc.
tion angle, and sometimes by making a The first entry in a note book each crook in the line owing to the transit morning should be the name of the per- being out of adjustment or level. Whenson acting as transitman, leveler orto- ever an observation of the pole star is pographer, as the case may be. All notes made, the variation of the needle should should be clearly and distinctly made in be noted. As the survey progresses, the pencil on the spot; no additional notes engineer in charge should project a locashould be entered with the original notes tion line on the map by means of the after the day on which the latter are cross sections taken to right and left, in written. Field notes should not be inked order to give a general idea of where the or changed in any way; copies of them true location of the road will be. Ile is may be made in ink and reduced levels expected to keep a diary in which to entered in ink. This is to prevent what note the progress of the work each day, is called “cooking” the notes, an of the difficulties overcome, and everything fence of which no true engineer is ever relating to the survey. He should see guilty. Any man found tampering with that the camp is properly supplied with the level notes or benches, or trying any everything needed, and should, if possischeme to make poor work pass for good, ble, have depots for provisions made at gets bis discharge without any compunc- points near which the line will pass, so as tion on the part of the chief engineer or to avoid packing them over the line. those who are interested in seeing work Camp should be moved every three or well done. A plot of the day's work four miles, in order to avoid long walks
to the place of starting work in the one) have been handed into the office, it morning. It may be necessary during is there decided what is to be the apthe progress of the survey to forward proximate location of the line. The special instructions to the engineer in party for location is the same as for precharge; for this and other reasons, that liminary, except that there is no explorer officer should take especial care that needed. The general style of the work whenever the camping ground is changed, is the same, the principal differences bea notice be distinctly written upon a tree, ing that, as the survey is a final one, the or in some other conspicuous position, centers are run in on the curves, and containing the following information: greater care is taken in getting the ele
1. The distinguishing letter of the vations of points between the stakes and survey.
on the cross sections. The subject of 2. The number of the camp.
curves is so well treated in Henck's Field 3. The date of removal of camp. Book for Engineers that it is useless to
4. The probable direction and distance go into it here. It will be sufficient to to the next camping ground.
state that the formulæ most often em5. The name of the engineer in charge ployed are T=Rtan 1 I and C=R tan I of the party.
I tan I, where T is the sub-tangent, R The success of the survey is materially the radius of the curve, I the angle of assisted by each man endeavoring to intersection and C the crown distance. save as much time as he can. A few The latter is used as a check for the corhints as to how this can be effected may rectness of the first half of a curve, be of use. Before moving the instru- which is so long as to require several
ment the transitman should, if he wish changes of instrument. The number of to prolong the line, set two pickets on stakes put in at one setting-up depends line beyond the new hub, in order that altogether upon the natural features of the axemen near continue their chopping the ground, the degree of the curve and while he is moving on and setting up the size and thickness of the timber. In He can set his own back picket, if it be running around a rocky bluff it may be left ready for him, by placing it close impossible to see more than one hundred behind the instrument and bringing the feet at a time, especially if the angle of cross to the level of the eye-piece. As deflection be large; in which case it soon as point for hub is called for, one of would be well to put in stakes fifty feet the axemen should commence making a apart. hub, and if the ground require it, legs In Plate I., Fig. 1, suppose the transit for the instrument. The fore chainman, to be set up at B to run in the curve who carries a light axe, should occupy BCDEF, &c., from the initial tangent himself in cutting stakes when not busy AB. If the points C, D, E and F are all chaining.
to be located from the point B, it will be There is a great variety of opinion as necessary to clear out all the timber on to what transit is the best for bush work. the area included between the chords Some engineers prefer those of English BC, CD, DE, EF and FB. Now if the manufacture, others those made in this curve be an easy one, that is of light country. The most satisfactory that I curvature, say thirty minutes, that area have ever tried is one of Gurley's man- will not be great, so that it would take ufacture.
| less time ordinarily to do that amount of chopping than to make a new set-up
at D, in which case the areas of the triAfter the results of the different pre- angles BCD and DEF only would have ļiminary surveys (if there be more than to be cleared. If the curve were heavy