98 The Library. the outgoing current distributed, that if you place the handker- chief or taper but a foot away from the grating it will hardly be seen to wave or flicker. In support of the efficacy of this method of ventilation, chemical observations have repeatedly been made with most satisfactory results. For myself, I can only speak of the results as they affect the organ of smell, but as I flatter myself that in that respect my sense is unusually keen, and that I take care to exercise it in all conditions, my testi- mony is not to be lightly esteemed. The effect of that testimony to the worth of the system described as a means of maintaining pure air, even in the most crowded room and on a muggy day, is distinctly favourable ; not less so is it to the merit of the system, already alluded to, of reducing to a minimum that great source of worry and trouble to all librarians, the floating dust in the atmo- sphere of our library rooms. With windows that cannot open, with doors through which when they are swung open the trend of the current is rather outwards than inwards owing to the com- pressed state of the internal atmosphere, and with the air that is forced into the room coming to us through a filtering screen, we have in the Public Library in Aberdeen, the luxury of an atmosphere as free from dust as probably is to be found in any public building in the country. And now for a few words as to the cost. The price of in- stallation here was about 800, but this is about ^"300 more than it would have been had its adoption been contemplated from the first, and the necessary structural arrangements made as the process of building went on. The daily consumption of gas for working the engine, for 14 hours a day, is about 600 feet, which at 33. 6d. per thousand feet amounts to a fraction under two- pence per hour. As for the cost of heating the building, ex- perience so far would show that the annual outlay in this respect would amount to ^"30 to 35, and when the area and loftiness of the chief rooms are taken into account, the charge seems small indeed. And yet I am not without hopes that, with a little more experience we may be able to reduce even this cost still lower. In conclusion, I have only to say that if I have succeeded in interesting any here in our experiment in Aberdeen in this department of library organization, it will give me much pleasure to show it in actual operation in the Public Library. A very little observation there will enable you to understand both the method and the merits of the system in a way that I could hardly hope to do by any number of words. A. W. ROBERTSON.
