The heads of the various departments make recommendations to the commissioner in charge of their respective departments, and each commissioner brings these recommendations to meetings of the board of commissioners, which are held on Tuesday and Friday of each week. The secretary to the board of commissioners records the action on these recommendations and acts as executive officer of the board by issuing orders and carrying on correspondence. Not all of the municipal duties are, however, vested in the board of commissioners. The management of the public schools is vested in a school board of nine members appointed by the justices of the Supreme Court of the District of Columbia. The Public Library, with its branches, is managed by a board of trustees appointed by the board of commissioners. The penal, charitable, and correctional institutions are managed by a board of public welfare appointed by the commissioners. The public utilities are under a public-utilities commission, consisting of two civilians, appointed by the President, and the engineer commissioner, who is a member ex officio. The public parks are under the jurisdiction of the Department of the Interior, which is also in charge of public buildings and grounds. The water supply is under an Army engineer officer, designated the district engineer, but the distribution of the water is under the jurisdiction of the commissioners. The zoning of private property as to height of building, use of building, area of ground to be built upon, is handled by a zoning commission, of which the three commissioners are members and, in addition thereto, the Architect of the Capitol and the Director of the National Park Service. The justices of the Supreme Court of the District of Columbia and the judges of the police, municipal, and juvenile courts are appointed by the President, as is also the recorder of deeds. The National Capital Park and Planning Commission has been created by Congress to advise the commissioners as to the planning of the city in laying out new and changing old highways. This commission purchases all land for parks and playgrounds. The land so purchased for parks is placed under the Department of the Interior and the land for playgrounds under the commissioners. All expenditures for municipal purposes, including the schools, parks, water supply, land purchases, etc., are appropriated by Congress annually, and are based upon estimates submitted by the heads of the District government and the other officials hereinbefore named.