REVIEW.

Otago Daily Times, Issue 3282, 13 August 1872, Page 3

REVIEW.

Trigonometrical Survey of the Province of Wellington, by Henry Jackson, Esq., F.R.S.S., Chief Surveyor.

This is one of the few papers that have lately emanated from the profession in New Zealand, that attract immediate attention, as a work of science and eminent practical utility. The paper also discloses curious facts in relation to popular opinion, which, in the above Province, seems to have been materially swayed by men generally called " practical" or, in other words, as the Auckland term goes, "intelligent chainmen." It is highly gratifying to see, at the same time, that the leading men in authority have protected and fostered the operations of which the paper is an account. In this respect their motives and vision are of the highest order. These Trigonometrical Surveys of Wellington, the author informs us, commenced in 1800, before which there were none deserving the name. We, ourselves, had an opportunity of glancing at the state of the various Survey departments in all Provinces of New Zealand several years ago, and may state that such was the state of all the offices. Canterbury and Auckland made an attempt at that time, it is true, in the direction of triangulation, but they might be placed in the same category as primitive Wellington, for in their execution they displayed none of the merits of this branch of surveying as a science, having been put together mechanically, and without mathematical reduction, as a child does the triangles and polygons of a Chinese puzzle—viz ,by "building." Speaking of New Zealand generally, it fell to the lot of Alexander Garvie, assistant-surveyor of the Otago staff - a carpenter by trade, a mathematician and practical astronomer by genius - to engage, under instructions, in the first trigonometrical surveying, properly so termed, and this in a locality the most remote in the Colony, viz., Waihopai (now Invercargill). This was in the year 1860. Herethe bearings were on the true meridian, the mean of nine readings; and the positions of stations are mathematically calculated on the meridian and perpendicular from an initial point. From this small beginning, and supported by the local authorities against the detracting influences of which Mr Jackson complains, the system then begun has extended its ramifications to almost every corner of the Province. So much we may speak of local matter.

From Mr Jackson's paper we perceive that his trigonometrical operations extend over 2½ millions of acres. By this means he has been enabled to overtake all settlement, and thus to control and submit to actual test not only much of previous surveys, but now to make his undeniably accurate data the basis of future section and block survey. He has thus attained for the area of the colony over

which he has the geodesical charge, this grand result, viz., that settlers may now invest their all in the labour of improving their land purchases, and so making a home for themselves and families without fear of being ousted by prior claims. He has overcome the inducements to the "make shift method" described by Wakefield, and in the good economy of his management has demonstrated most notably that the correct way is not more expensive than the haphazard one, while it is immensely more beneficial to the population, in the complete protection from lawsuits that it affords. He also saves to the Government of the country the constant re-arrangement of claims, the constant re-testing of boundaries, and the never-ending costliness of examinations into land grievances. The advantages thus secured to Wellington, have been secured at a cost of only £7000 - a mere bagatelle. Of the sectional survey, we are informed that he is now in a position to guarantee an accuracy of 1 in 1000. This is the same degree that is claimed from surveyors in this Province. Of this subject, in passing, we may remark that the Ordnance Survey of England still more requires an accuracy of about three times greater - viz., a foot and a half per mile. Thus the degree of accuracy claimed by the Colonial survey cannot be said to bear hard on practitioners, as it is easily effected by the competent and the honest, and to allow of less endangers the interests of the land-holders.

The results of the trianguiation of Wellington must be most gratifying to all engaged. Those appear elsewhere to have been questioned, but we would call them unquestionable; nor should we be backward in doing bo, seeing that the two field officers—Messrs Mitchell and Dundas - who executed the work, are Otago-bred, and the very beautiful map that illustrates the same is by our valued old friend and accomplished artist Mr Spreat. Following the very able reports that have lately been drawn up by the Secretary for Crown Lands and RegistrarGeneral, Mr Jackson's opportunely appears as a corollary. The holder of the former high offices, with opportunities of general information that no other oflicer possesses, has pronounced, that the safety of the Government of New Zealand itself, in guaranteeing lauded tenures under the new Act, requires that systematic and accurate survey should become a general, and not a load question. Also that the Survey Department should be maintained in its integrity as a scientific branch of the service, unobstructed by local influences and politics. In these sentiments we heartily concur, not caring by what means the desideratum maybe brought about, or how the service may be supported.

Of. the purely professional work we. will now say a few words. The arrangement of Mr Jackson's measures has no doubt been in conformity to the exigencies of his department, and the peculiar nature of his country. As a country for survey, Wellington presents a phase peculiari formidable; the greater credit to him who faced the difficulties. We observe that the three districts triangulated are on the magnetic meridian - a doubtful and changing one. To the professional surveyor, this fact, at the first glance, is unfavourable, but instantaneously only. In the mind of the merest charlatan alone would the impression continue. The second glance dispels what may have occurred to the mind, and the more careful and scrutinising the examination, so much the more is one convinced of the intrinsic merits of this very laborious undertaking; its thorough accuracy, its great detail, and its skilfulness in field observation, as well as profoundness of office calculation. Our objections to the magnetic meridian as a primary range for bearings is that it is ever changing, while the true meridian is fixed. Indeed, critically speaking, a survey can only be said to be on the magnetic meridian of a certain date. After that date, the primary bearings must be termed a range east or west. Further, a magnetic meridian, theoretically, cannot be produced in a straight line unless coincident with the true meridian, as the world is an oblate spheroid. On many accounts connected with goodesical survey and mapping, we would prefer the primary range on the true meridian - however, as affecting settlement survey, this does not matter. The practical work of Colonial survey can be founded on one as well as the other, and this is our principal object. In connection with this subject we would notice the very elaborate table of latitudes, longitudes, and magnetic bearings, from which latter data are given, with directions how to find the true bearings of the station. With the explanation, above given we need say no more about deducing the fixed from the unfixed, as it is done so accurately; we, however, would have preferred calling the Magnetic Bearing primary Range Bearings, as being more explicit and correct. In the table we perceive the full extent of patient labour that has been bestowed. To the uninitiated its cost of thought and perseverance will pass unappreciated, but in the estimation of his fellow-professionals this will not be so. Indeed, we have so high an opinion of this part of the publication, that we would rank it as an offering to pure science - a labour of love by a mind having a strong mathematical bias. We wish Mr Jackson every success in his further operations, fraught as they will be with benefit to, his fellow colonists.