All About Inventions and Discoveries
The Romance of modern scientific and mechanical Achievements

272 All About Inventions the air, but the majority of results proved im- practicable, principally because the electric current proved too expensive to produce. The great difficulty was not to produce a single spark, or series of sparks, such as Cavendish had employed and in such rapid succession as to resemble a con- tinuous pencil of fire similar to that produced in an ordinary electric arc lamp—a steadily burning electric flame. Sir William Crookes endeavoured to secure the required end, and, in 1892, demonstrated as an experiment before the Royal Society a flame of burn- ing nitrogen. This was nearly 120 years after the momentous discovery made by Cavendish. Sir William Crookes’ achievement prompted two French savants to attack the problem. They went a little farther because they were able to produce figures regarding the cost of producing a given quantity of nitric acid per hour. In this way it will be seen that the issue was rapidly being narrowed down to the pounds, shillings and pence aspect, otherwise the com- mercial possibilities of laboratory researches in this field. A decided impetus was imparted to the subject by the investigations of Lord Rayleigh in 1897. This famous chemist was engaged in a series of elabor- ate experiments which culminated in the discovery of argon, but incidentally, by reproducing the experi- ment of Sir William Crookes upon a larger scale, he was able to contribute more essential details concerning the cost of producing nitrates from the air. The following year Sir William Crookes returned to the subject. He emphasised the fact that the artificial production of nitrates was no longer merely