His most important labours, however, with reference to the arts, were his researches respecting iron and steel, which he published in 1722, in a separate work under the title of Traite sur l'art de convertir le fer en acier, et d'adoucir le fer fondu. At this period all the steel that was used in France was imported, none having previously been made in that country; and one may imagine how numerous and patient were the trials made by Reaumur before he succeeded in his object. The Duke of Orleans rewarded him for this valuable discovery, by bestowing on him a pension of 12,000 livres. In like manner, he found out the method of manufacturing tin-plate or whiteiron, which until then had been brought from Germany. In his various experiments, he had frequent occasion to observe that melted metals assume regular forms on cooling, and he accordingly gave an account of the crystallizations which they present. The manufacture of porcelain also engaged his attention, and received considerable improvements from him, although he did not succeed in perfecting it. In 1739, he made known a method which he had discovered of giving a whiteness and opacity to glass, which causes it to assume the appearance of chinaware. He was also the first who tried in France the expedient practised by the Egyptians for hatching eggs,--a subject which, being of a nature suited to popular apprehension, procured for him at least as much estimation as all his other researches. In Great Britain his fame seems to rest almost entirely on his peculiar scheme of graduating the thermometer. He chose the extreme points of the freezing and boiling of water, which, under similar circumstances, are always fixed and unvarying. The interval between these points he divided into eighty degrees, upon the principle that spirit of wine, in a certain state of rectification, expands 80,000 parts. In his experiments on this subject he arrived at some valuable conclusions, in regard to the varieties in their volume and temperature which are exhibited by particular fluids when combined, as well as on frigorific mixtures. He also carefully collected the observations on heat made in different places by means of his thermometer.