The north-westerly portion of the park, above the new reservoir, is planned very simply, in accordance with what we conceive to be the suggestion of the ground. The evergreen drive is continued nearly to the foot of Bogardus Hill, and then somewhat changing its character, turns to the east. At this point a branch road crosses a brook, that is made to expand into a pool a little below the bridge; and this road then winds gradually to the top of the hill, which offers an available site for some monument of public importance, that may also be used as an observatory tower. If as is not improbable, the transatlantic telegraph is brought to a favorable issue, while the park is in an early stage of construction, many reasons could, we think, be urged for commemorating the event by some such monument as the one suggested on the plan, and in study No. 9. The picturesque effect of a spring of clear water, that already exists in this vicinity, may be heightened, as suggested in study No. 10. The central portion of the upper section of the park is left as open as possible, and can be levelled so far as may be required for the purposes of the playgrounds indicated on the plan, and on study No. 7. At present, it is hardly thought that it would be necessary to make the Sixth avenue entrance to the north; but its position is indicated.[26] [26] NOTE, 1868.—The postponement of operations in this quarter was recommended because we found that the 106th street boundary of the park required a revision, which could not, with propriety be urged when the competition plan was made. The northern limit of the park was, subsequently to the date of this report, extended from 106th to 110th sts., and so much of the original plan as applied to the ground to the northward of that here described, was afterwards modified in order to connect satisfactorily with our design for laying out the additional territory which was approved by the commission in April, 1863. The north-east section of the upper park is shown as an arboretum of American trees, so that every one who wishes to do so may become acquainted with the trees and shrubs that will flourish in the open air in the northern and middle sections of our country. [Sidenote: The Arboretum.]