1865.] Sir C. Fox on the Pins of Chain Bridges. 139 



gitudinal sections. If my determination is correct, it represents (not 

 merely according to transcendental homological signification, but as a 

 simple question of plain anatomical observation) the whole of the great 

 transverse commissure, or corpus callosum of the lower placental mam- 

 mals, only in somewhat reduced proportions, and with relations somewhat 

 modified by the peculiar form of the inner cerebral wall. 



There is consequently no superadded structure in the brain of the latter 

 group. 



To the imputation, twice repeated, of having "obtained" or "derived" 

 the notions and ideas contained in my paper from Professor Owen's 

 writings, no direct reply is necessary. The communication which I pre- 

 sented to the Society is the result of repeated original observations and 

 dissections, made at various periods, extending over more than three 

 years. The descriptions are all verified by drawings and preparations. 



That their publication (if they should be so honoured) may advance in 

 some slight degree our knowledge of a difficult and obscure, yet important 

 branch of anatomy, is all that I venture to hope. That they are entirely 

 free from errors, or that they may not, at some future time, be superseded 

 by the researches of abler investigators, I do not presume to believe. 



II. " On the Size of Pins for connecting Flat Links in the Chains of 

 Suspension Bridges." By Sir CHARLES Fox. Communicated 

 by the President. Received March 2, 1865. 



In the construction of chains of this kind, it is of the highest importance 

 that the pins, which pass through and connect together the links of which 

 the chains are composed, should be of the right size, inasmuch as their 

 being too small, as compared with the links through which they pass, 

 renders ineffective a portion of the iron contained in the latter, which then 

 exists only as a useless load to be carried by such links ; while at the 

 same time, if the pins and heads of the links be too large, they become 

 uselessly cumbersome and expensive. 



Careful examination and experiments made upon a large scale (which 

 will be explained hereafter) have brought out facts by which a simple 

 rule has been arrived at a rule that may safely be adopted as a guide in 

 deciding upon the relative sizes of these two parts. 



On this rule mainly depends the economical use of iron in the con- 

 struction of such chains. 



In this paper the term chains for suspension bridges implies such as are 

 usually employed, and are composed of several flat bars of equal thickness 

 throughout, placed side by side, but having their ends swelled edgeways so 

 as to form what are technically termed heads, and which are coupled toge- 

 ther by pins passing through holes in such heads, as shown in figs. 5 & 6 

 in the accompanying drawing. 



In deciding upon the size of the pins, it has often been assumed, as 



