Nikola Tesla - Free-Energy Devices

178 INVENTIONS OF NIKOLA TESLA.But such a lamp would possess a vast advantage over an ordinaryincandescent lamp in regard to efficiency. It is well-knownthat the efficiency of a islamp to some extent a function of thedegree of incandescence, and that, could we but work a filamentat many times higher degrees of incandescence, the efficiencywould be much greater. In an ordinary lampthis is impracticableon account of the destruction of the filament, and it has beendetermined by experience how far it is advisable to push the incandescence.It is impossible to tell how much higher efficiencycould be obtained if the filament could withstand indefinitely,as the investigationto this end obviously cannot be carried beyonda certain stage but there are reasons for ; believing that itwould be very considerably higher. An improvement might bemade in the ordinary lamp by employing a short and thick carbon;but then the leading-in wires would have to be thick, and,besides, there are many other considerations which render such amodification entirely impracticable. But in a lamp as above described,the leading in wires may be very small, the incandescentrefractory material may be in the shape of blocks offering a verysmall radiating surface, so that less energy would be required tokeep them at the desired incandescence and in addition to;this,the refractory material need not be carbon, but may be manufacturedfrom mixtures of oxides, for instance, with carbon or othermaterial, or may be selected from bodies which are practicallynon-conductors, and capable of withstanding enormous degrees oftemperature.All this would point to the possibility of obtaining a muchhigher efficiency with such a lamp than is obtainable in ordinarylamps. In my experienceit has been demonstrated that theblocks are brought to high degrees of incandescence with muchlower potentials than those determined by calculation, and theblocks may be set at greater distances from each other. We mayfreely assume, and it is probable, that the molecular bombardmentis an important element in the heating, even if the globebe exhausted with the utmost care, as I have done for ; althoughthe number of the molecules is, comparatively speaking, insignificant,yet on account of the mean free path being very great,there are fewer collisions, and the molecules may reach muchhigher speeds, so that the heating effect due to this cause maybe considerable, as in the Crookes experiments with radiantmatter.