_Rules for calculation._ In a popular library, outside the reference room, for each foot of wall space available 80 books can be placed on eight shelves. Floor cases having two sides will hold 160 books for each running foot, and in a close stack 25 books, approximately, can be shelved for each square foot of floor space. But the latter rule will be materially modified by ledges, varying width of passages, stairs, etc. The above figures give full capacity. In practical work, to provide for convenient classification, expansion, oversized books and working facilities, the shelves of a library should be sufficient for twice the actual number of books and the lines of future enlargement should be fully determined. 2. _Departments._ Is the library for free circulation? Is the library for free reference? Are special rooms needed for high school students? children? ladies? magazine readers? newspaper readers? How many square feet for each of the above rooms? Are class rooms needed as in a college library? Club rooms? Lecture rooms? Museum? Art gallery? Other departments? 3. _Community._ In city or country? Population? By what class will library be chiefly used? School children? Students? Mechanics? Reading circles? Ladies? 4. _Resources and conditions._ Money available? Money annually for maintenance? Size of building lot? Location and surroundings? How many stories? Elevators? Heat? Light? Ventilation? 5. _Administration._ Is library to be in charge of one person? How many assistants? Is a work room needed? unpacking room? bindery? librarian's office? trustees' room? By careful study of these points a clear conception of the problem is gained and the building committee is prepared to draw an outline sketch indicating in a general way their needs and views. They are not likely to secure what they want by copying or even by competition. The best architects have not the time nor the disposition to compete with each other. A better way is to choose an architect, one who has succeeded in library work if possible, who will faithfully study the special problems, consult freely with the library board, propose plans and change them freely till they are right. And if such plans are also submitted for revision to some librarian of experience or to the library commission of the state, whose business and pleasure it is to give disinterested advice, so much the better. The following outlines taken from actual library buildings are offered by way of suggestion. _Square plan._