单项选择题

Although glasswares that were made in England dominated the early North American market,glassblowers from Great Britain were not easily persuaded to go to the North American colonies. The eighteenth century was the golden age of English glass: the industry and its employees prospered. Glassmakers were discouraged from emigrating because if English-quality glass were produced in the colonies the home industry would have been threatened. In one instance, five English glassmakers were arrested in England as they boarded a ship for America.
In spite of England’s disapproval of American manufacturing, an interest in glassmaking recurred periodically during the entire colonial era. The actual number of glass factories erected was small, only twelve or so, probably because the manufacturing of glass required a considerable initial investment in a large facility and a team of skilled workers. Glasshouses, as the glassmaking factories were called, could not be erected anywhere. Rather, sites had to be carefully selected on the basis of the availability of fuel and raw materials of very specific properties. The financial and technical considerations of glassmaking were such that most of the colonial glass factories lasted only a short time.
The colony of Pennsylvania was chosen as a site to make glass by several glass manufacturers. One glassworks was built there in the seventeenth century; at least six followed in the eighteenth. Pennsylvania’s first glasshouse was conceived in 1682 as part of the economic plan of the settlement of Philadelphia. For this undertaking an English window maker from England was hired. Four other English glassmakers agreed to accompany him. The founders of the settlement envisioned a glass factory not only to supply the demands for window and table glass within the colony, but also to provide goods for commercial trade.
The author indicates that the financial and technical considerations of colonial glassmaking resulted in _________.