There were many difficulties to be overcome before this pit-coal could be used with success. Greater care had to be taken in the selection of the materials for the pots—perhaps without the Stourbridge clay success would not have been attained—and it was found to be necessary to ‘close the pots,’ that is to say, to use a covered crucible so as to protect the glass from the smoky, sulphurous gases given off by the coal. The credit of the invention of these closed pots, with the mouth at the side facing the opening of the furnace, is also to be given to Percivall. I dwell on these practical details for a special reason. In the first place, the use of coal and the consequent change in the form of the crucibles mark the beginning of English glass as a distinct _genre_. Again, this change is closely connected with a further and still more important step—the use of lead as an essential constituent in a new kind of ‘metal,’ the famous English flint-glass of later days. It is these two novelties that form our contribution to the technique of glass-making. Not that I can find any proof that lead-glass was made in England at so early a date. But on the one hand the use of a covered pot rendered it more difficult, at that time at least, thoroughly to melt the contents, and therefore favoured the use of a more fusible mixture; on the other, in the case of a glass containing lead, it is above all essential to protect the ‘metal’ from the fire. The history of the progress of glass-making in England from the early days of Elizabeth to the outbreak of the Civil War in the next century, is chiefly concerned with the licences and patents granted to a succession of English and foreign ‘adventurers.’[240] No doubt there were many abuses in this system; but it is impossible to overlook the fact that the Cecils and the other advisers of the Queen were enabled by such means to encourage the foundation of many industries, and this chiefly by the help of foreigners. For at the beginning of Elizabeth’s reign we had fallen sadly behind in the matter of the industrial arts. Not only France and Italy, but Germany too and the Netherlands, had much to teach us. Already, however, before the death of the Queen and still more in the next reign, there arose, as I have said, a great popular outcry against the monopolists, and this feeling of indignation found an echo in more than one of James’s parliaments. It is the more strange, therefore, to find that it was during this reign that the whole glass industry of the country fell for the first and last time into the hands of one man. But this was no other than Sir Robert Mansell, Admiral of the Fleet, a man of exceptional energy and a born fighter, one who had in early life had more than one brush with the Spaniards. King James, when approached on the subject of Mansell’s glass monopoly, marvelled that ‘Robin Mansell being a seaman, whereby he hath got so much honour, should fall from water to tamper with fire.’