ECONOMY IN SURVEYING.

New Zealander, Volume 1, Issue 43, 28 March 1846, Page 4

ECONOMY IN SURVEYING.

To the Editor of thb New-Zealander. Sir, — For the public good, — three things connected with the Survey Department in New Zealand call for change; viz.— the Surveying instruments used, the method of forming Bouudary lines, and the description of those boundaries in the Deeds of Grant. To point out these defects, and feasible remedies, or saving com mutations, I essay the task as concomitant with the experience of the oldest practically colonial surveyor in these colonies, and in keeping with my suggestions and propositions in 1832, to the government and people of New South Wales, to reduce their Survey Department, (then at a cost to the revenue of per annum), and to survey Crown Lands by contracts ; the principles of those suggestions and propositions were mooted and carried in the first session of that Colony's representative members, and ever since have been acted upon, and the economical results therefrom, to their revenue maybe ascribed, the early introduction of those principles here; hence, 1 tender the underwritten remarks, &c.,for >our columns. General Rbmarks on Land Surveying in this Colony, contrasted withthatin other British Colonies. The prominent feature in this subject, is the unprecedently high cost incurred here for land surveying, when compared with that in any other of our colonies,— yet the Surveyor is paid the lowest in proportion to his services, here, to those of the Surveyor in other British colonies, but the useful object is to introduce to the notice of this government and the community, that method and instrument generally established, which are of far less cost for effecting the same thing, and equally efficient ; first, in British America, in New South Wales, Van Dieman's Land, &c, the costs of surveying lands in the former, is about four farthings per acre, in blocks of 80 to 100 square miles, (up- ! wards the cost is less), marked off in allotments of 200 acres each, and in the latter about two farthings per acre, in blocks of 100 to 150 square mile*, marked off in lots of 320, 640, 1280, and 2560 each. Here, previously to the government effecting the surveys of Crown lands by contracts, the average cost per acre was equal to Four shillings and Two pence, or 200 farthings ; i. c. seventy times more here than there, — and in the government notice of 28th Sept., 1842, (at the birth of those contracts), the proportionate price per acre, in 200 acre lots, is Bfd. a fraction over 8^(1. — this is a cost to this colony of more than B§d. to ]d. But in the schedule annexed to the said notice, the showing off, of the low cost per acre in the larger blocks, is not only arithmetically wrong, but wrongly advanced on the public, instance the 13th example, a block of six by twelve miles,— (this block, in retaining the half sections, ought to have been 6 1-16 by 12 1-16 miles, and the other large blocks proportionately increased to allow for the usual number of roads), the cost is put down at 2 farthings, whereas it is 2 \ farthings, making an error of £\2 0s Bd., in the amount of circumvallating said block at £3 per linear mile, now admitting that such block is found, which can for £3 a mile be measured, &c, in accordance with the official regulations : would it not be an insult to the understanding of any Georgick emigrant to tell him that this block was surveyed! or can it be said that such survey alone would in ihe least render such block available to the colonists ? Not until it shall have been d'vided into small farms, or colonial half sections, of 320 acres, such are the full average size of country allotments here, and them at £'-i per linear mile, its whole cost would be £972, (plus | of a mile for roads, 375. 6d.) and per acre, 5 1-I6d.— not 7d. as stated, for 320 acres, in said sched u^ c ! The causes for this high cost for surveying and l°w remuneration to the surveyor, arises from the general use of that inappropriate surveying instrument,— the Theodolite ; (an instrument happily adapted for general use in an old and populous country), and from the extraordinary method of forming boundary lines, here, similar to the original lines of a circumvallation m fortification, viz. by cutting them four feet wide, (vistas for the lints of colhmation), though heavily timbered, treuching, and forming hillocks at every quarter of a mile, or at every angle therein, often less than one chain distant, excavating two to four trenches at every principal corner, in addition to the hillock, forming picquets and poles, and placing 1 them in these hillocks, &c, which costs in timbered land from four to eight pounds per linear mile ; yet, young as this colony is, of many of those boundary lines, (in open laud), not a vestige remains ; these said causes of high cost become elucidated when the application of the said instrument and method of making boundaries in a new country, are compared with the bush eligibilities of the surveyieg instrument, the Cikcumfehentor, and the general method of marking boundary lines in those colonies ; by merely cutting out a chip fore and aft yf the line trees, and four chips quadraugularly out of the corner trees, which are quickly done and lastingly visible, but in open or bush land, the only marking is in driving appropriate stakes at the corners; this method for its sufficiency has stood the test of time. There also, the latter instrument for its adaption has superseded the use of all others in bush surveying, pi- marking off new lands, as with it the practical surveyor will dispatch three times the quantity of work in open land, allowing the courses or lines to be of ordinary lenglhs, and a much greater odds in wooded or timbered land, than he could effect by using the Theodolite, and pursuing the New Zealand method. The following comparative statement of the bush application of the two instruments may tend to show ■which of the two instruments is most eligible for the purpose ; at every station with the Theodolite, in marking a boundary line, &c, in the bush, much time is generally requisite in clearing away obstructions in the lines of sight, of both the front and back objects or station stavee, admitting no lines are to be otherwise cleared, at every station the adjustment of the instrument for horizontal motion and centrical position, also assistants to attend those staves; but to mark out such a line with the Circumferentor, l^ss than one-tenth the time for adjustment, none for clearing away, nor assistants with staves; further, the Theodolite demands unceasing attention to keep in effective order all its adjustments, if these are slurred over, the efficiency of the instrument is nullified. Again, the showing ot^the vertical arch, the proportional reduction of the hypotenusal to horizontal measurement, is oftener wrong than right, as on broken or uneven surfaces, the requisite stations for this instrument are very many, to eke data from which such showing is deduced, otherwise the errors resulting from the use of the chain on such surfaces cannot be obviated by the proportions on this arc, but when the using of the chain on any surface is resigned to ephemeral assistants, the adequacy of the instrument is neutralized,—the quality of the survey is in their keeping. Again the deductioi^for declivities, or acclivities, on even surfaces, are often insignificant, as the

angle with the horizon in either case, must be greater than eight (8°) degrees to require the reduction of one link in a chain; i. c. a fall or lise in the surface, of 9| feel in an advance of 66 feet, or one foot in 7 nearly ; and it may be affirmed that the efficiency of the survey depends as much on the care and judgment in using the chain as on those in using the instrument, and although this ought to be held an axiom in surveying, it is, in the colonies in this part cf the southern hemisphere, treated by surveyors as a menial manipolatinn. The Theodolite, in our colonies, has been heretofore applied solely to the most important surveys ; to laying out and subdividing town sites, and to trigonometrical operations, —and its expensive application, in common and small surveys in a new country, elicits no geodetical advantages, over similar surveys made by the Circumferentor and Pocket Sextant, as it cannot be justly concluded,— from the cutting up such country into small lots, even with the aid of the best instruments, but in many different hands guided by different capacities, will supply coincident data to connect the whole with approximating truth, »o as to exclude the necessity of a trigonometrical survey, of such country, ere a correct map of it can be produced. Although the surveyor can contemplate the Theodolite with complacence, it being the ne plus -ultra combination, in a structure of admirable mechanism, of the useful properties of all the other surveying instruments,— he cunnot vindicate its application as the work-a-day field instrument in a young and bankrupt colony.

Corollary. The head of that survey department who rejects the use of the Circumferentor, in the primary survey of a colony, subjects its government to uncalled for expense in his department, and its inhabitants to endless inconvenience relative to roads, &c, inasmuch that the most eligible lines for roads, cannot be known, laid out, or marked off, until the features of the colony are known in detail, viz.— a certain extent of its water boundaries, its rivers, creeks, gullies, ranges, <$■<:., are surveyed and mapped,— for such surveys this instrument has been and is held (in those colonies), the only one admissable, owing to the multiplicity of angles to be observed therein, the quickness of observing them with this instrument, and the facility of plotting them from the field book, —compared with the tardy processes in the field and office, resulting from the use of the Theoaohte.

An adjunct, of this extraordinary system of surveyiug, is the description of the boundaries of lands, in the deeds of Crown grants ; in these deeds there is no mention of'bearings of boundary lines ; the real causes of this, to be regretted omission, are not problematical ; first, the survey of the country commenced and continued with instruments as they came from the hands of the maker, and their magnetic results were naturally discouraging to the theoretically Precisian at the head of the department, the ordeal of assaying their qualities, or correcting their defects was too novel to be effected by the then Tyros in this professional department. Second, the avoidance of a prolix description of bearings in each deed, a description rendered thus by the unusuilly numerous angles formed, and distances measured in the curved and zigzag boundaries of land, especially, in the town crescents, quadrants, &c, and suburban allotments, the ultimate consequences of which must be, boundless disputes, if they are not occupied ere the surveyors' marks become obliterated,— for instance, ten years subsequent to satd marking, the boundaries of one of those allotments become contested, the surveyor will find nothing relevant in the deed, of the land it conveys, to enable him to settle the question at issue, hence, if the case be very important, his alternative must be a personal application at the Surveyor General's Office, (may be 1 to 200 miles off,) and what relevant data can he, or will he be allowed to glean there ? Augles j yes,—angles without subtending objects, equally futile as is a lever without a fulcrum ! The ostensible cause is, that all parties concerned in this omission, concluded that magnetic bearings are contradictory in themselves, hence, such parties decreed that such bearings should not be used even in the field, in reference to boundary lines, that the magnetic needle was often influenced by extraneous matter, that "this matter is so general in this colony, that here are but few places where the needle would not be thus attracted from the mugnetic meridian ; that agreement in the fore and back bearings oblerved from two stations, alternately, is a matter of chance, that of the many field instruments (theodolites,) belonging to this department, not any two of them agree in magnetic bearings, some differing from others as much as two degiees," &c. Thus inferring that the determination of the effects of magnetism' on the needle, or the action of a magnetised needle relative to the magnetic poles, is yet a desideratum ; — a metaphysical puzzle, beyond the pale of science ; yet it is so well understood, that the recession and retrocession of the magnetic poles on each side, alternately, of the true meridian, of many places, have been proved (as far back as observation goes, 200 years !) to be definite and nearly uniform, and can be nicely determined, relative to this meridian, to less than a minute of a degree, on almost every spot on terra fir ma. The evil of this omission would be limited principally to the Auckland district, if this variation were now to be annually determined and registered, and in lieu of independent angles, (if I may use the term), use magnetic bearings (from one quarter degree to 360 ° , without any other reference to the points of the compass, thus rendering their description concise and definite, an improvement introduced into Crown grants of Sydney, by Sir Thomas Mitchell,) of boundary lines of laud, and these entered in the Deeds of grant, will furnish data, which, with a starting point, will ever enable a surveyor to trace all the boundary lines with truth, but with the mdc. pendent angle, to be sought as above, he must have besides this starting: point, the two objects, or their correct positions, (?) which primarily subtended t his angle, — that he may thence find the concatenating angles of the whole boundaries. As to the discrepancies attributed to the actions of the needles ot the field instruments, of the survey department, that in observing the same objects at the same station with them, alternately, the magnetic angle pointed out by the needle and meridian of each instrument, differs more or less one from the other throughout, these disagreements are not confined to the needle, nor in any way influenced by ' extraneous matter,' yet the arrangement is la< ile, blending art with a little science, to cause them to work ill agreement, viz.— to determine the position of the line of sight, relative to the meridian of each instrument, respectively, thence, the concentricity or eccentricity of the ueedle, &c these will ensure coincidence in the use of these instruments in any other place. To accomplish this, is the primary and indispensable step to systematize and obtain corroborative materiel, from the geodetical operations of the many concerned. It is entering with truth the vestibule of professional science, — the precursor of efficient abilities in the head of a survey department.

And to further shew that such allegations, &c, as the above, are groundless, or emanate from ignorance, of the properties, or attractive power of materials relative to magnetism in the needle, and of practical knowledge of the use of the Cireumferentor, in particular. I submit to the public, the following statement of my experience with, and experiments on the magnetic needle during a reasonable series of years, which have opened fair premises to enable me to conclude that every dependmce in general may be placed on the action of the judiciously magnetised and well adjusted (centered and balanced), needle of the Circumferentor, or iuitably sized Theodolite, and that if it be so attracted, it must then be in thej immediate presence of s« me affinitious matter or substance, (as will be shewn), and allowing New Zealand to be a matrix of several minerals,— -yet of all the minerals, (42), on record, it is generally understood, that after each has been analytically formed into its respective mass, iron is the only one that has a strong affinity for magnetism, Jbut iron ore in its unearthed state will not attract the needle, though the instrument be stationed in its immediate vicinity. In the many observations, during more than eleven years practice in New Zealand, made at some thousand stations, with the Circumferentor, in various surveys, occasionally applying the Theodolite, from Knuckle Point, iv lat. 34|°, to the south of Mauukao, lat. 37% ° , and in the range, of l£° of long. The known region of minerals in this colony. Also in a trace survey, and in a trigonon etrical survey of the Bay of Islands, the first was made at or below high water mark, of all cu.stomary stations for a surveying instrument, the most mineralogically exposed, i. c., to the said ' extraneous matter.' The latter survey with the Theodolite, with which the to and fro, or back and forward bearings, or magnetic angles, connecting objects, were at every station minutely noted with their observed angles, on its graduated horizontal limb, and their greatest difference was from 3* to 6' minutes, where the wind did not affect the adjustment of the instrument ; and these angles ranged in every direction, over more than 200 square miles; the value of this approximation to coincidence in the action of the needles of the two instruments, was enhanced in deterrainining, by azimuths, that throughout these surveys, neither of the needles of the two instruments erred from the local magnetic meridian, as when the bearings did not coincide, the cause was in the judgment in apportioning the parts of the degree bisected by the needle, — and couple with the above, — the continued practice during more than thirty years, of usitig the Citcumferentor, &c, and of proving the variation in various places, in different countries, in each hemisphere, I trust will warrant my assertion that, by two judiciously observed azimuths of the sun, with a good Theodolite, in good working trim, the magnetic bearing of any line may be known, in defiance of mineralogical substances, at most to 10' or 12' minutes, in a survey however extensive, provided thas the concatenating angrle of such line, with either of the magnetic azimuths be known, hence alone, magnetic bearings of jmnioveable objects become known to perpetuity, or until the annihilation of their record, and are indispensable with consistency, in the description of boundaries, entered in any deed of land, and that such procedures of observations are the legitimate test of the needle's action, which is influenced more by metereological agents, than by mineralogical substances,— as generally, when I did not find my 'work to close,' J have traced the cause to those agents. A needle may be well balanced and centered, but confusedly magnetised;— an atmospheric influence may affect, or a magnetic dispersion possibly occur, in either case the careful surveyor will be warned,— the needle will display an obvious inertia ; and such I conceive to be the key to thejenigma of those nescientih'c allegations. To the above field experience, I add the following statement of some of the experiments made to test the needle's action in the immediate presence of affinitious matter, viz. — a magnet of ordinary power placed three feet distant, and in every direction relative to the instrument, did not during many trials affect the needle, and its greatest distance of attraction was 26 inches, neither pole of the magnet being retired. Therm. 76 ° . 2. Again neutralizing one pole of the magnet, and advancing the other towards the point of the needle, perpendicularly to the magnetic meridian, (the direction of the greatest leverage of attraction), the needle was attracted or repelled, alternately, as the magnet approached its relative or opposite side of the needle, and the greatest distauce of perceptible influence was two feet. Therm. 64°. 3. An anchor, (weight 34 lbs.) placed on a level, and in 8 positions circumscribing the Circumferentor, did not influence the needle at 28 inches distant, as four opposite bearings of objects were observed previously to the introduction of the anchor, aud also during each rest of this iron mass at its said various positions. The needle setled uniformly at the same points on the graduated circle, on directing the sight to the said objects respectively. I remain, Sir, Four's, &c M &c, T. FLORANCE, Hydrographic and Land Surveyor. Auckland, March, 24th, 1846.