if the star depart from the plumb-line, move the compasssight east or west along the timber, as the case may be, until the star shall attain its greatest elongation, when it will continue behind the plumb-line for several minutes, and will then recede from it in the direction contrary to its motion before it became stationary. Let the compasssight be now fastened to the horizontal plank. During this observation it will be necessary to have the plumbline lighted; this may be done by an assistant holding a candle near it.

Let now a staff, with a candle or lamp upon it, be placed at a distance of thirty or forty yards from the plumb-line, and in the same direction with it and the compass-sight. The line so determined makes, with the true meridian, an angle equal to the azimuth of the polestar; and from this line the variation of the needle is readily determined, even without tracing the true meridian on the ground.

Place the compass upon this line, turn the sights in the direction of it, and note the angle shown by the needle. Now, if the elongation, at the time of observation, was west, and the north end of the needle is on the west side of the line, the azimuth, plus the angle shown by the needle, is the true variation. But should the north end of the needle be found on the east side of the line, the elongation being west, the difference between the azimuth and the angle would show the variation, and the reverse when the elongation is east.

REMARK I. The variation at West Point, in September, 1835, was 6° 32' west.

REMARK II. The variation of the needle should always be noted on every survey made with the compass, and then if the land be surveyed at a future time, the old lines can always be re-run.

12. It has been found by observation, that heat and cold sensibly affect the magnetic needle, and that the same needle will, at the same place, indicate different lines at different hours of the day.

If the magnetic meridian be observed early in the morning, and again at different hours of the day, it will be found that the needle will continue to recede from the meridian as the day advances, until about the time of the highest temperature, when it will begin to return, and at evening will make the same line as in the morning. This change is called the diurnal variation, and varies, during the summer season, from one-fourth to one-fifth of a degree.

13. A very near approximation to a true meridian, and consequently to the variation, may be had, by remembering that the pole-star very nearly reaches the true meridian, when it is in the same vertical plane with the star Alioth in the tail of the Great Bear, which lies nearest the four stars forming the quadrilateral.

The vertical position can be ascertained by means of a plumb-line. To see the spider's lines in the field of the telescope at the same time with the star, a faint light

FIG. 7.

.

should be placed near the object-glass. When the plumbline, the star Alioth, and the north star fall on the vertical spider's line, the horizontal limb is firmly clamped, and the telescope brought down to the hori zon; a light, seen through a small aperture in a board, and held at some distance by an assistant, is then moved according to signals, until it is covered by the intersection of the spider's lines. A picket driven into the ground, under the light, serves to mark the meridian line for reference by day, when the angle formed by it and the magnetic

meridian may be measured.

WHEN DESIRED BY SETTLERS, SURVEYS MAY BE MADE BY THE SURVEYOR-GENERAL AT THEIR EXPENSE IN CERTAIN CASES.

It sometimes happens that for the purpose of perfecting their title at an earlier day, the settlers on the public lands prefer to pay for the survey of the township in which their claims are located, in order that it may be surveyed before the government is ready to make the survey in the regular progress of the public work. Congress has provided that this may be done when such townships are contiguous to some established lines of the public surveys from which the regular continuity of the surveys can be secured.

By section 10 of an act entitled "An act to reduce the expenses of the survey and sale of the public lands in the United States," approved May 30th, 1862, it is provided: "That when the settlers in any township or townships, not mineral or reserved by government, shall desire a survey made of the same under the authority of the Surveyor-General of the United States, and shall file an ap

plication therefor in writing, and deposit in a proper United States depository, to the credit of the United States, a sum sufficient to pay for such survey, together with all expenses incident thereto, without cost or claim for indemnity on the United States, it shall and may be lawful for said Surveyor-General, under such instructions. as may be given him by the Commissioner of the General Land Office, and in accordance with existing laws and instructions, to survey such township or townships, and make return therof to the general and proper local land office: Provided, The townships so proposed to be surveyed are within the range of the regular progress of the public surveys embraced by existing standard lines or bases for the township and subdivisional surveys."-(Sec. 10, p. 410, vol. xii. U. S. Laws.)

Applications for surveys under this law must be made. to the Surveyor-General in writing, upon the receipt of which he will furnish the applicant with an estimate of how much the desired survey will cost. On receiving a certificate of deposit of a United States depositary, showing that the required sum has been deposited with him in a proper manner to pay for the work, the Surveyor-Generalwill contract with a competent United States deputy surveyor, and have the survey made and returned in the same manner as other public surveys are.

The Surveyors-General are especially enjoined in all cases to state explicitly in their letters furnishing estimates to applicants, that the payment of the amount required for the survey will not give the depositor any priority of claim or right to purchase the land, or in any manner affect the claim or claims of any party or parties thereto; and that, when surveyed, it will be subject to the same laws and regulations in relation to the disposition thereof that other public lands are.

The money should be deposited to the credit of the Treasurer of the United States on account of the proper

appropriations. A separate estimate is required and a separate deposit must be made for office work and field work; one to be placed to the credit of the appropriation "for compensation of the Surveyor-General and the clerks in his office," and the other to the credit of the appropriation "for continuing the public surveys." The depositary will issue certificates in triplicate, one of which will be transmitted to the General Land Office with the contract and bond of the deputy surveyor.

The account will be adjusted and paid in the same manner as other surveying accounts. Should the amount deposited exceed the cost of survey and all expenses incident thereto, including office work, an account setting forth the fact of such excess may be rendered by the depositor, certified by the Surveyor-General, and transmitted to the General Land Office, with the final surveying returns, to be recorded for payment.

Where a township is surveyed under the provisions of the aforesaid act, the survey must include all the surveyable public land in such township.

CERTAIN SMALL ISLANDS MAY BE SURVEYED AT THE COST OF APPLICANTS.

In the early extension of the public surveys it frequently happened that small islands were omitted when the adjacent lands were surveyed. In the course of time as the country is settled these islands become more valuable, and numerous letters are received at the General Land Office from parties desiring to purchase, asking how they shall proceed to acquire a title to them.

The first step to be taken is to have such islands surveyed by an authorized government surveyor. When the islands are located in a surveying district where there is a Surveyor-General, the application for a survey should be made directly to that officer; should the applicant