Sayfadaki görseller
PDF
ePub

if they maintain the same length of pace the measurement would have to be reduced to the horizontal and a different correction would have to be applied to every different degree of slope, but by accustoming the students to take a pace a little shorter than their natural one (suppose their natural pace to be two feet seven, let them take a pace of two feet five), and they have one then that they can maintain under all circumstances. In going over level ground they would shorten their pace a little; in going up hill they would take their natural pace, which is equal to an artificial pace on horizontal ground. If they are going up a very steep place they would take a stick, perhaps, and measure the distance on the ground. It is found that this method gives a higher degree of accuracy in pacing than where an attempt is made to use the natural pace, or where an attempt is made to use a very long artificial pace. The pacíng survey is the introduction to determining the points of survey, and by it a student is taught to make many measurements. By pacing, the measurements can be made very rapidly, and the student can learn a great deal in measurements by a very little loss of time. The pacing survey is followed by a topographical survey in which the pacing survey is made with a level. Then he goes to farm surveys, and he learns to read all the bearings. Then comes the compass survey, after which the more accurate instruments, the transit and the level, are taken up. At first the instruments are thrown entirely out of adjustment; the student is required to adjust them perfectly. Then every morning before the student goes out to work he is required to run over the adjustments, make sure that the instrument is in good adjustment, and the result is that the student becomes pretty familiar with the instruments. The first exercise is the measuring of angle work by repetition. Known angles are taken and the students are required to measure these angles by repetition, making a large number of repetitions and determining the angle by dividing the last reading by the number of repetitions. This of course gives the result more accurately than measuring the angle singly, and as it has been already measured by more accurate instruments, the instructor is able to check the angle measured by the student.

Without going farther into details, it is the aim all through to make the course progressive, and to make sure that the students use correct methods from the very start, believing that if a student is allowed to go on with incorrect methods a day or two, it is very much more difficult for him to unlearn than to do it correctly in the first place. In all the traverses the purpose is to obtain the highest degree of accuracy, since less accurate methods can be easily learned by students, but he may not have an opportunity of learning more accurate methods in later life. In the traverse the students are required to repeat the angles, making several repetitions. Of course other methods of traversing are given, as with the telemeter, with continuous readings, etc.

One of the most valuable instruments used in the work, which has been used for seventeen years at Columbia, is the plane-table, already referred to. This

instrument is rarely used by engineers in the field, but as a method of instruction it is very valuable, teaching methods applicable to other instruments, providing the student understands them and has already used them in other instruments. Every student is required to make a survey of something like one hundred acres with the plane-table, putting in contour lines twenty feet apart and determining a very large number of points.

A hydrographic survey is made with a preliminary triangular survey and a large number of soundings; similarly with the mining survey and finally the rail

road survey

PROEESSOR BURTON thought that this question of economizing time in surveying was especially applicable just now. There is no place in the school course where time is more easily wasted than in trying to give adequate instruction in surveying. In the Institute of Technology of Massachusetts they are surrounded by just the same circumstances as those at Columbia College. They are in the city, and find it difficult to carry on surveys in the immediate vicinity, and the evolution there has been on lines similar to those in Columbia College. In the details of vacation work, however, they had had somewhat different experiences. He would first describe the way in which they had tried to meet the question of teaching surveying during the school year. In trying to economize time they had found that two things are very essential; first, that whatever weekly period is given to field surveying it should be continuous. They had done this by taking a day for surveying. This gives five hours continuous work. This day is so arranged that the next day's work following will be of a character that will not be affected by the fatigue of the students of the previous day as much as would ordinarily be the case. They also find that they can so arrange this day that when the weather does not permit of surveying, the time can be utilized without any loss in the regular routine of instruction, in the mathematical part of surveying, or in drawing. He placed great stress on this point, because he thought it was not brought out fully by Professor Monroe, that by putting the time together, whatever hours you have, you can manage to give during the school year much more instruction for the given number of hours than in any other way. He found by the tables given by the Engineering News, that the Institute of Technology gives about the minimum amount of time to surveying. He thought that they give fully enough. In the paper by Professor Jameson he found the time mentioned there as greatly in excess of anything they had ever thought of at the Massachusetts Institute. They find there that two hundred and forty hours in the whole course is sufficient, that five hours a week is ample to give instruction in the use of the simple surveying instruments, that is, the more common surveying instruments. The instruction in pacing, the instruction in the use of the chain, the compass, the transit, and the level could be given during the second or sophomore year of a civil engineer's course in one hundred and eighty hours, and even in a large city when it is necessary that a train should be taken by the students in order to convey them to a suitable location. Their experience had led him to believe that by arranging the work properly, this amount of time is sufficient for those studies. The most important consideration is the smallness of the divisions at the work and the number of instructors with the divisions. Professor Monroe had dwelt on the point of having a sufficient number of instructors with the students. They made a point of having a competent instructor with every party of three or four students. In this way he thought the work in the field can be carried on with as great economy of time as work in the laboratory.

The matter of checking up the work is also important, and they found a great economy of time is brought about by having different parties do their work in such a way that the final result is a combination of the work of all the parties. He emphasized the fact that it is possible within the regular school year, without taking more than this one hundred and eighty hours, to give adequate instruction in surveying with the chain, compass, transit and level during the sophomore year.

When it comes to the higher branches of surveying, he thought it necessary that the work should be done outside of the regular school year. He did not think it is possible to give adequate instruction in topographical and geodetic work in regular term time when the student is engaged in other work. Here the students must have time for continuous field work where

« ÖncekiDevam »