TABLE V.-Showing the corrected daily evaporation, daily amount of rain, and mean temperature at the several lake survey meteorological stations for different years.

The above Table V shows the evaporation, as corrected according to the before mentioned river observations, together with its relation to the rain-fall and temperature. The following table, VI, is compiled from the last, and gives the evaporation, &c., for the several lake stations, arranged according to their latitudes.

TABLE VI.-Showing the mean daily evaporation, amount of rain, and temperature at the several lake survey meteorological stations.

In the following Table VII is given the corrected mean daily evaporation, temperature, and rain-fall for each lake.

In the upper lakes these quantities are found by taking a mean of the different stations on the lake, but, as mentioned in the last report, we have no record of the evaporation on Lake Ontario, and, for that lake, it has been computed from the temperature and latitude, according to the ratio shown in table.

TABLE VII.-Showing the mean daily evaporation, amount of rain, and temperature for the several lakes.

The rain-fall in the preceding table is not taken from that given in tables, but from Table XXXVII, in the report on the outflow of the lakes, giving the rain-fall for the whole lake region.

but

That table was compiled from all the data to which I had access; Professor Joseph Henry informs me that he is about to publish a work on the rain-fall of the United States, compiled from the records of the Smithsonian Institution, which will probably contain much additional information on this subject, though it will hardly give what is most needed, the rain-fall of the country north of the lakes, and which would probably decrease the amounts given in table.

I remain, very respectfully, your obedient servant,
D. FARRAND HENRY.

Bvt. Brig. Gen. W. F. REYNOLDS,

Colonel Corps of Engineers, Detroit.

APPENDIX Y.

OFFICE OF PUBLIC BUILDINGS, GROUNDS, AND WORKS,

United States Capitol, Washington City, D. C., August 1, 1869. GENERAL: The accompanying annual report, in relation to the preparation of the different maps of campaigns and battle-fields which were compiled from the field-notes of surveys made under my direction, is respectfully furnished for your information. The maps, including all those portions of the country over which the surveys have actually been extended, and which comprise, with one or two exceptions, the entire field of operations of the contending armies from Antietam to Appomattox Court House, have been completed.

The first of the series of maps prepared exhibit principally the movements of the army south of the Rapidan; and the last ones, which have just been finished, comprise several of the battle-fields north of that river and along the Rappahannock; Antietam and Harper's Ferry are included among them.

It may be interesting to give a brief recapitulation of the work, its arrangement and extent, and to offer a few suggestions as to a plan for its future continuance and completion.

The surveys cover an extent of nearly fifteen hundred square miles. The following statement furnishes a list of the number of maps which have been prepared, comprising a portfolio of one hundred and eightysix sheets:

1. The general maps, two inches to the mile, represent the reduced detailed surveys of the country between Cold Harbor and Appomattox Court House, numbering thirteen sheets.

2. The detailed maps are on a scale of eight inches to the mile, twentynine in number; eight of which represent the intrenched lines in front of Petersburg, and the remainder those around Richmond and along the James River.

3. Sixteen sheets, scale of four inches to the mile, exhibit the most prominent battle-fields, comprising Fredericksburg, Chancellorsville, Wilderness, Mine Run, Todd's Tavern, Spottsylvania Court House, North Anna, Tolopotomy, Cold Harbor, Five Forks, Jetersville, Sailor's Creek, Farmville, Appomattox Court House, Harper's Ferry, and Antietam.

4. Thirteen sheets, one inch to the mile, show the original maps issued at the commencement of the campaign of 1864.

5. Three sheets of sections of those last mentioned, corrected and distributed on the march.

6. One hundred and eleven drawings of forts, redoubts, batteries, and mines, the scale of the respective plans being forty feet to one inch.

7. The index map, scale 5000, is a general map of the country lying east of the Alleghany Mountains, and extending from the battle-field of Gettysburg, on the north, to the South Side railroad, on the south.

The material collected during the surveys has been entirely exhausted. The general map, which is intended to accompany and form an index for the detailed sheets, is still in course of construction. Its completion has been delayed in consequence of the absence of the correct data to enable a connection to be formed between the several surveys that have already been made; this can only be obtained by a further prosecution of the field-work. Reference is respectfully made to the recommendations that appear in my last annual report, and to the plan proposed in a communication on the subject which was addressed to the Chief of Engineers on the 7th of last May. In that letter it was stated that the colored portions of the general map which accompanied it, "present a

diagram of the theater of operations; certain spaces exhibit the sections already surveyed and mapped, and others present the additional localities which should be surveyed in order to prepare and complete the sheets necessary to fully illustrate the history of the several campaigns." The party, as organized by me in the summer of 1868, surveyed in fortysix working days an area of one hundred and eighty-eight square miles, comprising the battle-fields of Fredericksburg, Chancellorsville, Wilderness, Mine Run, and North Anna. A similarly organized party should, according to past experience, be able to survey about one hundred square miles per month. As there still remain between nine hundred and one thousand square miles, it will require from nine to ten months to complete the field-work. Could the necessary transportation be temporarily furnished by the officers of the Quartermaster's Department at such military posts as may be convenient to the work, and could subsistence be supplied from the nearest subsistence depots, the cost of the survey would be very considerably reduced. The necessary rodmen, instrument bearers, and flagmen of the party could be detailed, as formerly, from the engineer battalion. The pay and incidental expenses of the principal and assistants of the party would be alone required to prosecute the work. An appropriation of fifteen thousand dollars is respectfully asked for the same to be applied during the coming year. I am, general, very respectfully, your obedient servant, N. MICHLER,

Major of Engineers, Brt. Brig. Gen. U. S. A.

Bvt. Maj. Gen. A. A. HUMPHREYS,

Brigadier General and Chief of Engineers,

Office of the Chief of Engineers, Washington, D. C.