On the Ventilating and Heating System of the Aberdeen Public Library. 1 " I "HE subject of the ventilation and heating of libraries having - already at the Reading meeting in 1890 been before the Association, it is unnecessary for me to discuss the general merits of the question. Whatever else we may differ upon we are at least agreed in desiring to have in the interests alike of health, comfort and cleanliness, the maximum of fresh pure air with the minimum of discomfort, dust and expense throughout our library rooms. Towards this end the Committee of Management of the Public Library in this city, following in the wake more par- ticularly of one of the large infirmaries in Glasgow and of several of the Aberdeen Board Schools, adopted a system which has been attended with highly satisfactory results, and of which, therefore, I wish to give you some account. At the outset I would explain that the system in question is of the kind called the " mechanical system," and as such is to be distinguished from what may be called the " natural system." Further it is a mechanical system by impulsion as distinguished from that by extraction. As a mechanical system it undertakes by means of suitable machinery, to supply throughout the building a constant and controllable supply of fresh purified air, which is warm in winter and cool in summer, and to do this irrespective of the natural conditions of the external atmosphere. In this way it seeks to overcome the defects which are inherent in every so- called natural system of ventilation, whether it takes the primitive and prejudicial form of partly opened windows, or of the less objectionable, but still disadvantageous form of a system of inlet and outlet tubes. For all such methods have the radical objec- tion that they are dependent for their action on the condition of the external atmosphere, and that they cease to operate, or operate injuriously when these conditions are unfavourable. As 1 Communicated to the Sixteenth Annual Meeting of the Library Association, Aberdeen, Sept., 1893. 9
