In earlier ages the typical Englishman had lived much by himself; his home was his castle, and in it he developed his intense individulalism; but in the first half of the eighteenth century some three thousand public coffeehouses and a large number of private clubs appeared in London alone; and the sociability of which these clubs were an expression was typical of all English cities.请重点解释一下最后半句的结构。

在年青的时候这个具有典型代表性的英国人独自生活了很久；他的家就是他的城堡，他在这里养成了他强烈的个人主义；但是在十九世纪前半叶，大约有三千个公共咖啡馆和大量的私人俱乐部唯独在伦敦出现；这些俱乐部是对社交的表现是所有英国城市的典型代表。
of which these clubs were an expression 是一个定语从句修饰the sociability 。these clubs were an expression 这些俱乐部是一种表现。即是对sociability（社交行为）的表现。the sociability of which these clubs were an expression was typical of all English cities.在这句中sociability 又是主语，谓语是was typical of all English cities。