So when acetylene gas mixed with other gases is passed over a catalyst, such as a heated mass of iron ore or clay (hydrates or silicates of iron or aluminum), it forms all sorts of curious combinations. In the presence of steam we may get such simple compounds as acetic acid, acetone and the like. But when three acetylene molecules join to form a ring of six carbon atoms we get compounds of the benzene series such as were described in the chapter on the coal-tar colors. If ammonia is mixed with acetylene we may get rings with the nitrogen atom in place of one of the carbons, like the pyridins and quinolins, pungent bases such as are found in opium and tobacco. Or if hydrogen sulfide is mixed with the acetylene we may get thiophenes, which have sulfur in the ring. So, starting with the simple combination of two atoms of carbon with two of hydrogen, we can get directly by this single process some of the most complicated compounds of the organic world, as well as many others not found in nature. In the development of the electric furnace America played a pioneer part. Provost Smith of the University of Pennsylvania, who is the best authority on the history of chemistry in America, claims for Robert Hare, a Philadelphia chemist born in 1781, the honor of constructing the first electrical furnace. With this crude apparatus and with no greater electromotive force than could be attained from a voltaic pile, he converted charcoal into graphite, volatilized phosphorus from its compounds, isolated metallic calcium and synthesized calcium carbide. It is to Hare also that we owe the invention in 1801 of the oxy-hydrogen blowpipe, which nowadays is used with acetylene as well as hydrogen. With this instrument he was able to fuse strontia and volatilize platinum.