4. Bay windows
The second marquess of Bute, as lord of most of the manors of east Glamorgan, owned the minerals not only beneath his freeholds, but also beneath the commons within the basin of the river Taff, commons which stretched almost precisely to the northern limits of the coalfield. It was during the survey of the estate commenced in 1817 that Bute began to appreciate the wealth that could accrue to him through the exploitation of the coalfield.  By the 1830s, when the second marquess embarked on the dock building project which was aimed at bringing that 'enormous wealth, estimated to represented £375 million in royalties ,into 'full activity'.  Having been awakened to a realisation of the value of his inheritance, he hastened to secure his rights over what he already owned and to enlarge his holdings within the coalfield through purchase.
Substantial purchases of mineral land were made, some aiming at the command of openings to the commons in places where surreptitious enclosure had created a barrier between Bute freeholds and the waste, and others representing significant extensions of the marquess's property within the coalfield. The Rhondda estate of Sir John Wood, purchased in 1824, included the land upon which the township of Treherbert was later built, and the Wyndham Lewis property in the Cynon valley, acquired in 1826, comprised much of the site of the town of Aberdare.  These purchases initiated a policy which was to continue throughout the nineteenth century, and which made the Bute family the owners of by far the largest estate in the valleys of the Taff, the Rhondda, the Cynon and the Rhymney, the richest part of the coalfield. In 1919 the fourth marquess stated that the family had spent £220,000 on purchasing mineral land in the south Wales coalfield between 1814 and 1919, purchases which were among the most profitable investments made by any landed family.  From this time the industrialisation of the coalfield and the associated urban development of the pastoral valleys may be regarded through a series of conceptual windows between the valley lands of the Glamorgan uplands, with their underlying coalfield, and Cardiff Bay.