=133.= Lending library barriers for open access are planned in a variety of ways to take charging trays, etc. The following are typical illustrations of barriers or combined counters and screens specially designed for open access libraries. The object of the glazed screen is to protect the staff from draughts and the charging system from being tampered with. The plans and views of open access barriers in Figs. 24-25 show the usual arrangement for ordinary purposes, and an imaginary design for a library doing a very large business requiring three assistants at each side is shown in Fig. 28. By means of this it would be possible for six assistants, three at each side, to discharge and charge books at the rate of 1400 per hour, a speed never required anywhere. For all practical purposes a barrier with two wickets on the entrance side and one at the exit will serve for the largest single library in existence (Fig. 27). The treadle latches such as are fitted in the open access libraries of Croydon, Clerkenwell, Hornsey, Lambeth, Darwen, Southport, etc., will be found well adapted for the purpose of controlling the wickets of both single and double open access barriers (Fig. 29). [Illustration: FIG. 26.--Lambeth (Herne Hill) Branch Library Open Access Barrier (Section 133).] The chief objection to wickets hinged at one side is their tendency to slam, no matter what kind of controlling springs or buffers are used. In course of time every form of pneumatic or other spring loses its power, and some effective form of noiseless turnstile or very light barrier on rising butts would perhaps be an improvement. Where lending libraries are isolated, the trouble is not so marked as in cases where they adjoin reading rooms. =134.= The plans already printed (Figs. 18-22) explain better than words the form of counters best adapted for lending libraries using the indicator system of issue. The space for borrowers in front of an indicator ought not to be less than four square feet per person likely to be present at one time, in order to prevent crowding at busy times. Thus a town with 3000 borrowers would have an average daily issue of about 300 volumes, which might mean seventy-five people present at one time, counting companions, and thus 300 square feet of borrowers’ lobby would be necessary as a minimum; or a space 30 by 10 feet. It is not often, however, that one finds lobbies planned on this desirable scale. The height of a counter designed to carry an indicator should not exceed thirty inches, and the top need not be more than eighteen inches wide. The length of the counter will depend entirely upon the kind of indicator used, and whether it is classified or not, or intended for all the stock or only for fiction. The indicators most used all differ in size (see Section 386, etc.), and this factor must be taken into account in designing the counter.