was that of economies of scale. Those more successful areas at that time had plentiful easily accessed reserves which encouraged investment and the sharing of fixed costs such as harbour facilities, buildings and machinery among a large number of enterprises.

The early situation changed as the operators in the valleys exhausted the cheaply extracted ores and found themselves having to mine deeper and also further away from the rivers that were used for transport, thus increasing their costs per unit of coal mined. Some coal was probably