408 MERIDIAN SURVEYING. [April 



MERIDIAN SURVEYING. 



THE " dumpy leveller " of our youth, then in the front rank of 

 professionals, soon fell on evil days, obliging hiin to practically 

 amplify the genius of George Stephenson across the seas. Here, 

 again, individual misfortunes have only proved national oppor- 

 tunities. For the most daring examples in construction in recent 

 railway practice have been on the model of foreign or colonial 

 examples ; while now it would appear that we are to be taught 

 accurate laud surveying from the methods of the New Zealand 

 Government specialists. This is the main purport of a work just 

 published by Mr. William Tenman, C.E., now of Edinburgh, entitled 

 land Surveying on the Meridian and Pcr^Kudieular St/stem, 

 London, E. & K Spon ; and the author argues that we might 

 advantageously base our measurements of small estates by chain 

 and theodolite, by first finding the meridian position of the spot 

 in question with the aid of sun observations by the latter instrument, 

 according to this system, going into the methods of survey, plotting, 

 and computation in a very clear and painstaking fashion. 



Foresters will find this book specially useful, because their 

 surveying approximates to that pursued by colonial engineers. In 

 the section on layiug off roads, Mr. Penman shows, most explicitly, 

 how the ordinary method of traversing and ranging parallel lines 

 of equal width may involve very serious errors; and contrasts the 

 merits in this particular of the new method. Further, on areas, 

 plotted in ordinary fashion of 12, 20, and 13 acres, with detailed 

 roods and poles, errors of 8, 4, and 5 poles were shown to have 

 been consummated when calculated according to the meridian and 

 perpendicular system, which after all is no mystery, as it rests on 

 the self-evident fact, that the distance obtained from one point to 

 another must be checked by another way of effecting the same 

 computation, the discrepant numbers otherwise showing erroneous 

 surveying. 



The book is admirably adapted for self-instruction ; having, 

 besides many woodcuts, a beautifully-coloured plan of an estate 

 showing the tyro how to finish his work. 



