Vol. XII. No. 302. 



THE AGRICULTURAL NEWS. 



381 



STUDENTS' CORNER. 



INFORMATION CONCERNING LAND 



MEASUREMENT. 



In the measurement of land one of the first essentials is 

 to possess a knowledge of the rules fer determing the areas 

 of simple rectilineal figures. 



THE UECTANOLE AND r.VRALLELOGRAM. 



It may be pointed out first of all, that it is very impor- 

 tant for the student to remember the difference between the 

 figures known respectively as a rectangle and a parallelogram. 

 A parallelogram may be described in popular language aa 

 a rectangle pushed out of shape by the application of pressure 

 at one corner. The area of a rectangle is obtained by 

 multiplying together the length of two adjacent sides; the 

 area of a parallelogram, on the other hand, is ascertained 

 by multiplying the base by the perpendicular height. 



RULES FOR COMPUTING THE AREA OF A TRIANGLE. 



The most important figure with which the land 

 surveyor has to deal, is the triangle. The area of this figure 

 can be found by multiplying the base by one half the 

 perpendicular height. There is a second rule, however, which 

 is often useful when the tree sides of the triangle are given, 

 namely: from half the sum of the three sides substract each 

 side separately; multiply the half sum and the three remaind- 

 ers together: the square root of the product will be the area. 

 The area is always computed where possible by the first rule. 

 In cases where it is required to find the area of an irregular 

 rectilineal figure, all that is neces.sary in the case of, say, 

 a four-sided figure, is to draw a diagonal, determine the areas 

 of the two triangles thus formed, and add these two areas 

 together. 



THE .-iUKVEYOR's CHAIN AND IT.S USE. 



The measurement of land is generally done by means 

 of a chain, a chain survey being one of the simplest 

 kinds of survey work. A chain is 100 feet long and is 

 divided into 100 links. In using the chain two assist- 

 ants termed the 'leader' and 'follower' respectively are 

 required; the leader takes the handle of the chain in his left 

 hand and iron arrows in his right, and moves ahead while 

 the follower remains at the starting point looking at the 

 poles in front of him that have been set up to mark the lines 

 to be measured, directing the leader into line by signs with 

 his left hand They then move ahead and repeat the opera- 

 tion until the line across the field is measured. The figures 

 are entered up in what is known as the field book. 



MEASURING FLAT AND SLOPING GROUND. 



The setting up of the poles to show the lines to be 

 measured is based on the theory of triangulation, which will 

 be dealt with in due course. }5efore proceeding to this 

 subject it is necessary to explain the difference between 

 measuring flat ground and sloping ground. The student will 

 appreciate the importance of Ihi.s part of the subject by 

 considering what allowances he would make if he had to 

 measure a field of provision crops or young cacao situated on 

 the side of a hill or on very undulating ground, compared 

 -with a survey of a similar field on perfectly flat ground. 

 A plan is a horizontal representation of the features of the 

 ground. All measurements must therefore be reduced to 

 a horizontal plane. Any undulations of the ground can be 



shown on what is known as a 'section', a term commonly 

 used in connexion with levelling A plan is, therefore, not 

 the actual surface of thu ground, but the diminished 

 quantity that would result were the whole i)roiected on 

 a horizontal plane. In ri.sing or falling ground, the slope 

 represents that side of a right-angled triangle opposite the 

 right-angle, and is conseqaently of greater length than 

 another side of the triangle, i.e , the horizontal distance. 

 If the slope be not very steep, the horizontal measurements 

 can be obtained by holding up horizontally, as nearly as 

 can be judged by the eye, a part of the chain, .say 2-5 

 links at a time, and allowing a pointed plummet to 

 mark the measurements on the surface, this operation being 

 continued until the undulating ground is measured. This 

 method is known as 'stepping', and is recommended aa 

 being generally sufficiently accurate for small surveys. 

 The steeper the slope, the less the length that can be 

 measured by each holding up of the chain. 



Another method is for the surveyor to judge the angle 

 of slope, which is generally between 5 and 20 degrees, 

 and to set back the arrow the number of links specified in a 

 table which shows the necessary reduction. Sometimes the 

 angle is determined with a clinometer or other angular 

 instrument. In ordinary estate work, however, the 

 'stepping' method should suffice. 



RESUME. 



In the foregoing article the student will understand 

 that the main objeit has been to lay down some of the first 

 principles of out ofdoor surface measurement, and to 

 indicate as clearly as space will allow, the difference between 

 measuring sloping land and fiat land. Further information 

 on the subject will be given in a future issue of the Ajri- 

 cultural iVeJt's. 



DEPARTMENT NEWS. 



The Imperial Commissioner of Agriculture 

 returned to Barbados by the S.S. 'Korona' on 

 November 1.5, 1913, from an official visit to St. Lucia. 



In addition to matters of routine, attention was 

 given to questions connected with the working of the 

 lime juice factory which began operations on November 

 11. Reunion estate was visited in conne.xion with the 

 Experiment Station and Land Settlement, together 

 with Marquis estate where developments are taking 

 place in regard to limea and cacao. 



Mr. H. A. Baliou, M.Sc. Entomologist to the 

 Department also i-eturned by the same steamer after 

 conducting investigations in Dominica. 



Mr. P. H. Lamb, Diirector of Agriculture, Northern 

 Nigeria: Mr. D. W. Scotland, Assistant Director of 

 Agriculture, Sierra Leone; and Mr. K. Gill, an 

 Assistant Superintendent of Agricidture, Southern 

 Nigeria, arrived in Barbados by the R.M.S. 'Orotova' 

 on Monday November 17, 1913, with the object of 

 making official visits to this Office, previous to 

 proceeding to other islands for the purpose of 

 studying agricultural conditions in the West Indies. 



