IA TEXT-BOOK OF THEODOLITE SURVEYING & LEVELLING.

Otago Witness, Issue 2860, 6 January 1909, Page 81

I A TEXT -BOOK OF THEODOLITE SURVEYING & LEVELLING.

YOU THE I"SE OF STUDENTS IN LAND AND MINE SURVEYING. R' - James P\p.k, P-uf'.^s.-ir nf jimmy: Engineering, Director oT Ot.igo Univcr^ ty School of Mines, etc. (With 91 illustrations and two plate-.*. j London : Charles Griffin and Co. (Ltd.), Dunedin : Whii combe and Tombs (Ltd.), R. J. Stark and Co., pnd Braithwaite's Book Arcade. (7s 6d.) (Reviewed by Dixosnis.) This book covers the course of .«tu*ly : ami practical work laid down for mining and engineering ,?tudent<> and for survey , cadets who intend to git for exr-maiatinn 1 for diplomas as licensed surveyors. It progres.-es by easy ctages from the simple to the complex, the matter being specially ad- pit d for life both at Home and in the colonies. The subject is treated throughOHt in accordance with the mode of procedure now known as the new system of fcurveyina, which i>ims at mathematical ■fxa-ct'tude. as oppoeed toHhe old system by which only close approximations could be obtained. In trder to properly undeistand the scope o£ the book it may be nece.-sary to explain that the old system of surveying depends mainly on the use of the compass and Gunter chain for the field observations, and the protractor for the representation of the work on piper. In the n-fw system the work is based on the observing of angles with the theodolite, tho measurement of distances -nith carefully standardised steel-bands, trigonometrical an:l co-ordinate methods of plotting and computation. In the former the bearings are read from the magnetic meridian, which does not point in the same direction in any two places, and, moreover, is liable to a daily and yearly variation. In the latter ths bearings are referred to the true meridian, which is invariable, thus preventing, as we gather from the text, the overlapping of boundaries and the errors that are inseparable from work done according to the old system. Trigonometrical surveying has been in use in India and the colonies for over a I quarter of a century, and in its application to land and mine surveys has, perhaps, reached a higher degree of refinement here than elsewhere. It will doubtless come as a surprise to many to be told that the survey practice of England is a generation behind that of New Zealand, yet such is the acknowledged fact, and hence also the reason for the British Government employing New Zealand surveyors when work has to be done in 1 accordance with the new system in Singapore, Burmah, Borneo, Central and South Africa, and other dependencies of the Empire. I can very well recall the surprise and incredulity with which I first heard this statement as made to me by Mr C. W. Adams, late chief surveyor of Otago. Old usages die hard in England, and in respect to land and mine surveys the compass method still holds the fort?. Except in connection with the admirable triangulation of the scientific branch of the Royal Engineers, theodolite surveying is almost unknown in the land and mine surveys of the United Kingdom. The backwardness that exists in this important branch of professional work is now becoming recognised, and in the past few years the universities and mining schools of England have dovetailed the new system with the ' old with the view of eventually eliuiin.it1 ing the latter. The text-books on, surveying published by English authors deal at great length J with the old system, giving elaborate descriptions of instruments and methods that have long been obsolete in the colonies. A demand has long existed for a practical manual on the new system of surveying, and the present work by Professor Park is the first to meet this requirement. The 1 book has already received warm rom- ' mendation from high authorities both at Home and in the colonies, and although I cannot claim a professional knowledge j of surveying, still I venture to think that I it will be found to more than fulfil the 1 expectations of the author. It is certainly ' no mean compliment to him and to Otago ; University that London should come to New Zealand for the highly-specialised class of university text-books that have ' come to be associated with Professor 1 Park's name. For a teacher to write a J book for his own class is one thing ; but to write a book that is acceptable to university professors throughout the Engli?hspeaking world is an achievement that can only be attained by meritorious work. To' write several such works falls to the lot of a few, and' I think I am right m .saying that the sterling value of his works on mining geology, the cyanide process, etc., with his many memoirs, causes Professor Park to be more often quoted in foreign scientific literatu-e than any other author in this hemisphere. I The work before me is divided into 14 ' chapters, dealing with the theodolite and j ita adjustment.-, steel-bands, meridians, bearinys. field-procedure in traversing and triangulation, levels and levelling, contouring, mine-purveying, etc. The chap- , ter on practical astronomy, treating of the determination of the true meridian, latitude and time, is particulaily full and clear, the formula; and figures being adapted both for tho northern and >outhern hemi.*phero. The definitions of Mich astronomical terms as declination, rieht ascension, polar distance, convergence of meridian, parallax, etc., are so dimply put as to be readily understood even by the unprofeasioijal layman. To compute the position of a, star and to find it by daylight as a pin-liead of light in its place in the field of the telescope must surely be a source oj muc-h satisfaction to the observer. The grading of f .\stftter-races ; running pi oohx/OMx% the mo-

clem practice of conducting mine surveys and 01 carrying the time meridian into' mines, and the. survey pf bore-holes, .ira. a'A dealt with in a dear and comprehensive manner. A rueful and, to the student, a valuable feature of the baok is the large number of woiked-out examples of actual observations with which each problem in surveying is illustrated. The unit of measure used in modern surveying is tie chain, equal to 100 links. An acre contains 10 equare chains, or 100,000 square links. The system is practically a decimal one, and ite use is so simple as to be delightful. But" mart the ineptitude of the present-day- boaks oji arithmetic when dealing with mensuration, a subject that is an every-day requirement. A perusal of the 'books used in our public schools, both primary and seeordar/., phows us that the authors are sublimely ignorant of the fact that the units of . square jax-dis, square furlongs, etc., with which pupils are tortured and bewildered aw as dead as the dodo, and have to*~be\ unlearned outs.de the school door. .^ljSrsa^ o\-er, irroguW nrc^s of land aTe not now, as fjhown in these books, computed by plotting and dividing up into convenient triangles, which gives en approximation only, hut by the application of a simple method of giaphs without plotting, by v.bieh the area can be obtained wit,'i mathematical exactness. Ths art of surveying is merely a branch of applied mathematics, in which we "find the application of many well-known: principleß and problems the utility of which is often puzzling to the pupil, and, for the most part, unknown to the master, and even to the writer of school text-booke. Because of they light It throve upon these matt-ers there need be little hesitation in saying that this book will not or.'y Do welcomed- by students in surveying and .i? tronomy. surveyors and en.gireer.«, but also by the mastem of primary and sec whiry schools, who will be the better ;or know- ! ing something of the applic-no'i of the [ first principles they are railed u[;on to teach. The fact that this book emanates from the celebrated publishing house of Charles Griffin and Co. is sufficient guarantee that it is all it should be from a publisher's standpoint. The type is clean, clear, ard opes, wliile the nunierous diagrams are. models of lucidity, reproduced" 4et4i»sjMi>*feM style.