94 



THE FARMER'S MAGAZINE. 



THE ORDNANCE SURVEY— A CADASTRAL MAP. 



A correspondence is going on in the daily papers be- 

 tween Lord Elcho on tlie one band, and Sir Roderick 

 Murcbison and Mr. Locke on tlie otber, respecting the 

 second vote of the House of Commons, by which tlie 

 twenty-five inch mapping of the Hcottish Ordnance 

 survey on a scale of twenty-five inches to the mile has 

 been abandoned. Our opinion respecting the natural 

 advantages of an accurate territorial as well as geogra- 

 phical survey are on record ; and we cannot but regret 

 the abandonment of the large scale on the Scottish sur- 

 vey, which we hoped some day to see extended to Eng- 

 land as a substitute for that very imperfect one — the 

 tithe survey. The imperfections of that survey arise 

 from its having been executed by the individual 

 parishes and proprietors, instead of under some central 

 authority. The result is that scarcely one-third of 

 tithe maps are fitted for the purposes of valuation or 

 registration ; as they might have been at even less ex- 

 pense to the proprietors if conducted by the Govern- 

 ment on one uniform plan, but paid for by the land- 

 owners. 



While regretting the abandonment of the survey of 

 Scotland on the large scale, we are quite willing to 

 admit that this is one of those questions on which there 

 is a great deal to be said on both sides, and which is 

 fair subject for a compromise. The compromise which 

 we would recommend is this — that the survey should 

 proceed in as great detail as would be required for a 

 map on the twenty-five inch scale ; that no map but 

 that on the one-inch scale should be published, but that 

 the extra expense required for the surveying and map- 

 ping on the twenty-five inch scale should be defrayed 

 by an assession on the land. In return for this special 

 tax imposed on the land, each landowner should be 

 furnished with a certain number of copies of his pro- 

 perty, prepared by the lithographic or anastatic pro- 

 cess. The following points may be accepted as indis- 

 putable :— 1. That the one-inch scale is the best adapted 

 for geographical purposes. 2. That the six-inch scale 

 is too large for geographical, and too small for terri- 

 torial and property purposes. It originated in Ireland 

 at a time when the county cess was the only tax on the 

 land, which was levied, not on individual farms and 

 fields, but on townlands, as the unit of taxation. A 

 townland, it may be as well to remind our English 

 readers, varies in size from less than one hundred to 

 more than three hundred acres. As soon as the poor- 

 law was introduced into Ireland, a moi-e minute survey 

 became necessary, which should embrace every field. 

 Why, in England and Scotland, should we adopt a scale 

 which is too small for measuring the contents of fields, 

 on which the writing cannot be read without a magni- 

 fying glass ? 3. Another undoubted fact is that the 

 expenditure for the ordnance survey, and, we may add, 

 geological survey, may be regarded as a mere advance 

 of money, to be ultimately repaid by the sale of the 



maps. The Government geological survey has hitherto 

 been conducted with the one-inch maps, because in the 

 districts over which it has extended there were no others. 

 As soon, however, as it proceeded into counties mapped 

 on a larger scale, the six-inch scale was found superior 

 to the one-inch, and the twenty-five-inch superior to 

 both, although the only geological maps which will 

 ever be published are reduced to the one-inch scale. 

 By the anastatic process, therefore, that survey might 

 be furnished with copies of the twenty-five-inch scale 

 for their working plans, while they would only publish 

 the results on the one-inch scale. In former articles, 

 we stated the annual amount derived by the Govern- 

 ment from the sale of the Ordnance and geological 

 maps, and we have reason to believe that since then the 

 sale of both has considerably increased. But while 

 we give all due credit to the geological maps of the 

 Government as maps of classification, it cannot be pre- 

 tended that they include all the information that a land- 

 owner should possess respecting the soils, subsoils, and 

 substrata of his estate; or that such information can 

 be recorded in an efficient and satisfactory manner on 

 a map on a smaller scale than that of the tithe survey, 

 or, better still, the more perfect maps of the Ordnance 

 Office. 



The time has not yet arrived when landowners are 

 aware of the advantages they would derive from such a 

 minute examination of the soils, subsoils, and substrata 

 of their estates; but it will arrive before another gene- 

 ration has passed away, and there will be plenty of de- 

 mand for the Ordnance maps on the largest scale from 

 every proprietor of an estate. 



Mr. Locke, in his letter, talks of imaginary lines on 

 the Ordnance maps. The weak point of the survey 

 is that these lines of equal altitudes are not, and can- 

 not, be defined on the ground by permanent marks. 

 Far superior to these would be the method advocated 

 by Colonel Dawson, in his evidence before the House 

 of Commons, to which we have already adverted. 

 He proposed that instead of these lines of equal 

 elevation, of v/hich no permanent trace can be left 

 on the ground, the elevation of certain fixed points 

 should be determined and recorded on the ground, from 

 which a landowner who desired it, or the engineer 

 constructing a road or railway, or requiring to ascer- 

 tain levels for draining and other agricultural pur- 

 poses, would bo able to construct contour maps for 

 their own special purposes. Colonel Dawson proposed 

 that level-marks should be made on permanent objects 

 easily determined and easily found, both along the 

 lines of drainage and of the lines of watershed. He 

 would have such altitudes recorded, for instance, on the 

 mile-stones, sills of church-doors, &c. These would 

 serve as fixed points, to which those who required more 

 detailed levellings might refer for that datam line. 



There is one important point connected with a cadas- 



