The ironwork by which these chains are attached to the desk is somewhat complicated. By the kindness of the librarian, Signor Guido Biagi, I have been allowed to study it at my leisure, and to draw a diagrammatic sketch (fig. 107) which I hope will make it clear to my readers. The lock is sunk in the central support of the desk. The bar passes through a ring on each side of this support, and also through a ring near each end of the desk. These rings are fixed to the lower edge of the desk just under the molding. A flat piece of iron is forged on to the bar near the centre. This iron is pierced near the key-hole with an oblong slit through which passes a moveable piece of iron, here shewn in outline of its actual size (fig. 108). The bolt of the lock passes through a hole in this piece, and holds the bar firmly in its place. [Illustration: Fig. 107. Diagram to explain the ironwork at the Medicean Library.] [Illustration: Fig. 108. Outline of bolt forming part of ironwork.] The bar is not quite so long as the desk; consequently, when it has been unlocked, and the iron bolt sketched above withdrawn, it can be turned round by taking hold of the central iron, and pushed to the right or to the left, past the terminal rings. The chains can then be readily unstrung, or another strung upon the bar. In the next chapter I shall describe the changes in Library arrangements adopted during the period which succeeded the Middle Ages; but, before ending this present chapter, there are a few points affecting the older libraries and their organization to which I should like to draw attention. In the first place all medieval libraries were practically public. I do not mean that strangers were let in, but even in those of the monasteries, books were let out on the deposit of a sufficient caution; and in Houses such as S. Victor and S. Germain des Pres, Paris, and at the Cathedral of Rouen, the collections were open to readers on certain days in the week. The Papal library and those at Urbino and Florence were also public; and even at Oxford and Cambridge there was practically no objection to lending books on good security. Secular corporations followed the example set by the Church, and lent their manuscripts, but only on security. A very remarkable example of this practice is afforded by the transaction between the Ecole de Medecine, Paris, and Louis XI. The king wanted their copy of a certain work on medicine; they declined to lend it unless he deposited 12 marks worth of plate and 100 gold crowns. This he agreed to do; the book was borrowed; duly copied, and 24 January, 1472, restored to the Medical Faculty, who in their turn sent back the deposit to the king[423].