ancient names by stating that the "barbarous and uncouth names of places in Ireland much retard the reformation of the country, and directing "the Lord Lieutenant and council to change such names into others more suitable to the English tongue, annexing the ancient names in every grant so altered." These directions were embodied in the acts of explanation, but we may well sympathise with Lieut.Colonel Larcom when he observes that, "few persons will now be found to regret that the change of names thus authorized and ordered was not generally carried into effect." In the Ordnance Survey the importance of a correct determination of names was felt and fully appreciated, and "Name Books" were established by Major Colby, in which the officers entered the names, according to the best information they could acquire; but the enquiry did not rest here, but became the subject of the most careful antiquarian research. Lieut.-Colonel Larcom, who took so active a part in this and other branches of the survey, observes in respect to names, that, "as for the orthography of the names engraved on the maps of the Ordnance Survey, the different spellings and alias names of every townland were collected from all accessible documents, some (where the names were ancient) of very great antiquity; and finally, local inquiry and examination were made by an Irish scholar on the spot, to render the name ultimately adopted as nearly as possible consistent with the ancient orthography. This information being all classified, and arranged in proper descrip

tive books forms a large collection of documents, which, being preserved with the records of the survey, may be at any time referred to or published; and as there is scarcely any more fertile source of confusion than uncertainty of nomenclature, it may be hoped that as the boundaries of the Ordnance Survey are recognized by several Acts of Parlia ment, the names now engraved on the authorized maps of that survey, may also become generally adopted in all legal and authentic papers." Had the Survey Memoir, commenced with so much promise in the Memoir of Templemore, been extended to the whole country, these names would, without doubt, have been published in connection with their meanings as interpreted by Dr. Donovan, and have shel much light on the earlier history of the country. Accustomed, indeed, as we are, to the use of names which have, during the lapse of ages, gradually undergone so many changes as to have lost all resemblance to their originals, we are too apt to undervalue the importance of clearing away the disguise and tracing out the real and graphic name which lies beneath it, and is in itself a record of some local peculiarity or some historic fact. General Colby was no antiquarian, and the attention he directed to this special object is therefore a strong example of the sound good sense and judgment he exhibited even in subjects to which he had not previously directed his attention.

MODE OF SURVEYING.-In the early surveys the system was that of "simple surrounds," as it was

called, the perimeter of the ground being measured by a chain, aided by the compass or circumferentor, and the area being determined by measuring the figure of the ground, when plotted on paper. Such a system could afford no check against the errors so likely to occur in measuring the perimeter, as the work might close pretty well at the end and yet be affected by many intermediate though compensating errors. In the 11th Article therefore of the instructions issued by Dr. Petty to his surveyors, he enjoined them, " by intersections, to determine the true places of all townes, churches, castles, knowne houses, hills, raths, &c., within each respective surround, and to be frequent in making such observations, for the better examining and correcting your works;" and thus a system of checks was introduced to guard against the possible distortions of the measured perimeter. In the 5th Article of his additional instructions, Dr. Petty provided even for a check upon the truthfulness of the Field Books, as he directs, "as to the trueth of the field books, you shall, as often as you see occasion, cause some angles or sides, or both, to be measured (unknowne to the measurer unto whome the measuring thereoff is allotted), thereby to examine any sophistication of the said field books ;" and in the oth, he directs that "the common lines of each barrony are to be run together by two distinct measurers at once, their respective servants keeping double reckoning of the chains alsoe;" whilst in the 7th he explains the mode of applying the checks in plotting; thus,

"As often as conveniently you can, you shall protract your large surrounds before you doe the inworke of the same; neither shall you allow of such inward lines as you have taken by intersection from the outmeares, untill the said outmeares bee approved of by protraction; and when you shall correct any worke by tyeing lines, you are to select and run for that purpose such lines as may alsoe subdivide the said great denomination into its several properties and qualities, according to the rule aforegiven."

These instructions manifest a great improvement in the mode of survey, as compared with the "surrounds," which had been before used without any system of cross or traverse checking. In the Ordnance Survey, "surrounds" when necessary for the measurement of roads, &c., became secondary, and dependent on the internal triangulation, as in this work a complete and regular triangulation was estab lished, from the great triangles depending upon and proceeding from a base line measured, as will be hereafter shown, with all the precision of modern science, down, through various gradations, to the minor triangles, the sides of which were required to be measured with the chain. In such a system as this all must depend upon the fidelity with which the field work has been executed and recorded; and the most effectual mode to ensure such fidelity, was to separate the duty of calculating, and of protracting the angles and lines, from that of observing and measuring the one devolving on the field parties, and the other on the office computers and draughts

men.

Some misconception seems to exist in the minds of surveyors as to the advantage of this division of labour; which, indeed, they have looked upon as derogatory to their profession, inasmuch as it degrades, in their estimation, a surveyor to the rank of a mere mechanic. In such cases the ordinary pride of man being enlisted against the judgment of a man of science, has, as might have been expected, produced many partial and much exaggerated opinions, the error of which becomes apparent on the very slightest examination. Beginning, then, with the great triangulation, it is evident that the field observer can seldom do more, in the way of calculation, than roughly work up the data of the few triangles he requires for protracting his own general diagram. He sends then his observation book, with a diagram explanatory of the approximate positions of the objects, to the computer, and if the latter experience any difficulty in making use of either of these documents, the fault must be ascribed to the observer, who has either wrongly exhibited the objects on his diagram, or has made mistakes in observing or recording their angular positions. To every one accustomed to the observation of distant terrestrial objects, the difficulty of recognising with certainty every member of a cluster of mountains, of which the relative positions change in respect to every observing station, must be familiar; and though this difficulty may be greatly diminished by the point-fixer furnishing the observer with a rough diagram of all the objects of importance surround