Jim had a relative attending classes at Cooper Union and encouraged me to join several of its evening classes, which I did. I reported to him regularly the new things which I learned there. This practice benefited me even more than it did Jim, because in trying to explain to him the laws of heat phenomena, which were explained to me in the evening lectures at Cooper Union, I got a very much better hold of them. The first ideas of sound and light I caught on the pasture-lands of my native village; the first ideas of the phenomena of heat I caught in the boiler-room in Cortlandt Street and at Cooper Union lectures. These lectures, supplemented by Jim’s boiler-room demonstrations, proved much more effective than the instruction which I had received from my teacher Kos, in Panchevo. Kos was a Slovene, a native of that beautiful valley in Carniola, in the very bosom of the Dolomites; it is nearer to being an ideal dreamland than any other spot in Europe. To Kos, as to every true Slav, and particularly to the Slovenes of Carniola, the poetical side of physical phenomena appealed most strongly. Hence his patient listening to my enthusiastic professions of the belief that sound and light were different forms of the language of God. But as I watched the busy flames under Jim’s boilers, and understood how they were sustaining the strenuous efforts of steam to supply every hustling wheel in the factory with driving power, I understood for the first time that there is also a prose in physics not a bit less impressive than its poetry. It is this prose which interested Jim, the fireman, just as it did the Cooper Union lecturer. Their chief concern was what heat can do and not what it is. My Slavonic craving for knowing what heat is was soon satisfied by reading a poem in prose concerning the nature of heat. But of that later.