J846.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



357 



hedges and be numbered on both sides from different ends." This number- 

 ing on both sides is unnecessary, if Ihe staff be divided into 10 parts, the 

 centre having a double line : a little practice will make it perfectly familiar 

 without the figures. The link-staff is best made of round ash, divided as 

 above with a red hot wire, instead of painting or cutting ; it should be shod 

 Tvith iron, and have a small hook and spike attached to the top ; the diame- 

 ter at bottom should be about one inch and taper (o | at the top, and the 

 hook and shoe should be included in the measurement, namely, within a 

 fraction of C feet 8 inches for the whole length. 



The field book is hkewise described in the old fashioned manner, having 

 figures merely to the off-sets, without sketches. It is invariably the best way 

 to sketch in the work on each side of the line as nearly as possible to resemble 

 the objects to be delineated, and although it may take a little more time in 

 the field, the labour is well spent by its assisting the memory in plotting. 

 His system of " naming" the lines by their length, viz., " 6S5 on 731" is 

 confusing ; it should be according to the page upon which the number is 

 found, viz., "685, folio 47," and a circle should be made round the figures 

 which are intended for stations. It is hkewise vei-y serviceable to the memory 

 to surround those stations that run from, or across, the base line with a 

 triangle, instead of a circle, which will be found to act as a useful index. 



.\ chapter upon the reduction of customary to statute measure, and vice 

 versa, will be found useful, — 



" Rediietion of Customary to Statute Measure, and vice versa. — The statute 

 length of the perch is 16 and a half feet, but it is different in various coun- 

 tries of England. 



In Devonshire and Somersetshire, the customary perch, that is, the local 

 measure of the perch, is less, being but 15 feet. 



In Cornwall, it is more, 18 feet ; while in Lancashire, it increases to 21 ; 

 and in Staffordshire and Cheshire it is as much as 24 feet. 



This is a lineal difference. There is, also, in some counties of England, a 

 superficial difference in the measure of an acre ; an acre, in Wiltshire, con- 

 taining only 120 square statute perches, instead of 100. 



The Wiltshire customary acre is, therefore, one quarter less than the statute 

 acre, and the rood one quarter less than the statute rood. 



As property is frequently bought and sold by the customary measure of 

 the county wherein it lies, the surveyor is often called upon to reduce it from 

 one to the other. 



Different Values of the Acre. — The number of (statute) square yards in an 



acre, will, of course, vary with the length of the customary perch of the 



county. — (--Vn acre consisting of ten square chains or of 160 square perches.) 



In the statute acre, a square perch is 272'2j square feet, and the acre, 



therefore, is equal to 



272-25 X 160 = 43360 square feet, 

 = 4880 square yards; 

 In the acre of Devonshire or Somersetshire, as the square perch contains 

 15 X 15 square feet, or 225 square feet. 



the number of square feet = 225 x 160 = 36000 

 and of yards = 4000 

 In Cornwall, where the perch is IS feet, 



18 X 18 = 324 X 160 feet= 31840 square feet. 



or 5 760 square yards. 

 The Lancashire perch is 21 feet long; the square perch, therefore, must 

 contain 21 x 21 =441 square feet, which will make the acre to contain 70,560 

 square feet, or 7840 square yards. 



The customary acre in Cheshire and Staffordshire is the largest of the 

 whole, each perch being 24 feet ; the acre will consist of 24 x 24 x 100 square 

 feet, which is equal to 92160 square feet, or 10240 square yards ; while the 

 Wiltshire acre consists only of J the statute acre, or 3630 square yards. 



To reduce Statute Measure to Cnstomart/, or one Customary to another. 

 Rule I. — Bring the acres, roods, &c., in every case, to square perches ; 

 multiply these by the number of square feet in the given perch to bring them 

 into square feet (a foot being the common unit of measurement of both 

 statute and customary measure), and divide by the number of square feet in 

 the required perch; this will bring it into perches ; raise these perches to 

 roods and acres and the result is the area in acres, roods, and perches of the 

 customarj' measure required. 



Example 1. — Reduce 25 acres, 2 roods, 16 perches, statute measure, to 

 the customary measure (Derbyshire) of 15 feet to a percb. 



25a. 2r. 16p. = 4096 statute perches, 

 but the square feet in a statute perch = 272-25 ; 

 • . • 4090X 272-25 = 1115136 square feet. 



Whence 111513 6 1115136 cust. perches. 



15x15 "^ 225 = 4956 = 30a. 3r. 36 P. 



Ans. 30a. 3r. 36^. Derbyshire measure. 

 To bring customary into statute measure, reverse the preceding rule. 

 Example 1. — How many statute acres are there in 28 acres, 3 roods, and 

 15 perches, of Devonshire measure ? 



2Sa. 3r. 15p. = 28-843 75 Devonshire acres 

 if the Devonshire acre = l ; the statute acre = -826447 statute acres, 

 whence 28-84375 x -826447 =23-8378 = 23a. 3r. 14p. 

 Ans. 23a. 3r. 14p. 



Scotch Measure. — The acre in Scotland consists as in England of 10 square 

 chains, (each chain divided into 100 links,) and is reckoned in acres, roods, 

 and falls, which are equivalent to the English perches ; 40 falls making one 

 rood, and 4 roods one acre. The Scotch chain, however, is 8 feet longer 

 than the English, being 74 feet instead of 66. 



The acre being 10 square chains = 10 x 74'* = 54760 square feet. 

 -\na as 10 square chains = 160 square perches, 

 54760 feet 

 ^ =one square perch ; 



Therefore one square perch or =342-25 square feet. 



7'o bring English Statute Measure into Scotch. 

 Rule 1. — Reduce the given area into English perches, and then into square 

 feet by multiplying by 272-25, the number of square feet in an Enghsh 

 statute perch ; divide this product by the numlier of square feet (342-25) 

 there are in a Scotch fall, and you obtain the area in terms of Scotch falls, 

 which bring back to their proper quantities in loods and acres.* 



* To briog Scotch measure into English, rererse the preceding rule. 



Example 1. — Reduce 32a. 3r. 25p. English statute measure, into Scotch 

 measure. 



32a. 3r. 25p. = 5265 square perches. 

 272-25 X 5'205 = 1433396 square feet in the given area. 

 And dividing by 342-25 = 4188 square falls = 26a. Or. 28p. 



Ans. 26a. Or. 2Sp." 



The Theodolite is next described with some examples of its use ; then 

 follows the CiRcuMFERENTOR, apothcr old fashioned instrument, which, by 

 most London surveyors, is superseded by the theodolite. 



Examples are shown for laying down " the variation of the needle," but 

 unless it can be precisely ascertained at the date of the survey, it is much 

 better to omit it and show the magnetic bearing only — for inasmuch as the 

 variation of the needle is different in different countries, it is safer to put the 

 needle-bearing only, which answers all practical purposes. Many other hints 

 and examples follow which may be more or less useful to the beginner. 



The treatise on levelling is of the usual description, but does not give suf- 

 ficient examples, omitting for instance, all mention of cross sections, that 

 mostly puzzle the beginner. The author describes the staff-holder as " hav- 

 ing considerable responsibility reposed in him." We advise therefore that this 

 duty be simplified as much as possible, and in order to facihtate the most 

 important part of it, that of keeping the staff" upright, there should be at- 

 tached two small spirit levels placed at right angles on the staff', one being 

 at the back and the other on one side, about four feet high from the ground. 

 Some levellers attach a circular bubble at the back, which answers the same 

 purpose, also a handle for holding the staff without conceaUng the figures. 

 The staff-holder should also carry a small iron tripod to place under the 

 staff whenever used — this should not be attached to the staff, for it is re- 

 quisite sometimes to leave it, whilst observations are being made with the 

 same staff", at other plac s. It is always adviseable to level with two staves ; 

 when one only is used there is much liability to error, for should the instru- 

 ment be out of adjustment or ba turned it round, there is no means of again 

 taking the back set. The bubble must always stand in the middle whenever 

 the level is turned round or the work will not be correct. We mention this 

 on the knowledge that many levellers neglect it, considering it of no im- 

 portaiice so that the bubble is in the centre when the observation is made. 



Origin and Reclamation of Peat Bog, with observations on the Construc- 

 tion of Roads, Railways, and Canals in Bog. By Bernakd Mcllins, 

 C.E., Vice-President of the Institute <f Civil Engineers of Ireland, and 

 M. B. MuLLiNs, A.M., C.E. Dublin : Oldham, 1846 ; Svo., pp. 48 ; five 

 lithographic plates. 



This treatise contains the subject of a paper read before the Institute of 

 Civil Engineers of Ireland, and the result of long professional experience, 

 makes its appearance opportunely at the present time, when the e.xecutioa 

 of public works iu Ireland attract peculiar interest. 



iNIany fallacies are exposed in the present work. It seems to be shown 

 pretty clearly that bogs are the cause, uot the effect, of the destruction of 

 ancient forests ; that, in fact, the accumulated vegetable matter which 

 covers one-seventh of tlie area of Ireland (nearly three millions of acres) 

 does not arise from the decay of trees, but from the bog moss, which only 

 fiourishes iu comparatively cold climates, and entirely different from the 

 vegetation of the morasses of warmer couutries. 



The absurdity of the recommendaliou iu various Parliamentary Reports 

 not to drain too deep is successfully shown, and the value of draining by 

 deep drains for purposes of agriculture aud also for the construction of 

 solid foundations of roads and railways is considered at length. Messrs. 



