180 SECTIONAL ADDRESSES. 
more economical than any electromagnetic machine. I am not quite confident 
about this, but shall be so soon, as I am getting a large voltaic, and I shall 
soon learn how expensive its habits are, and multiply by the number 
required for a lighthouse.’ This was thirty-two years after Faraday had 
discovered the principle of the dynamo. 
In after years Kelvin lost his dread of the commutator and championed 
direct against alternating current on every possible occasion. In 1879, 
when giving evidence before a Select Committee of the House of Commons 
on Electric Light, he even assured them that there would be no danger of 
terrible effects from the employment of electric power, because the currents 
would be continuous and not alternating ! 
The fifteen years following 1863 saw a great development of the dynamo, 
and in 1878, when a paper was read before the Institution of Civil Engineers 
on the improvements introduced by Siemens, Thomson made a remark, 
following a suggestion by Dr. C. W. Siemens, that showed that he had by 
this time thoroughly grasped the possibilities. He said that he believed 
that with an exceedingly moderate amount of copper it would be possible 
to carry the electrical energy for one hundred or two hundred or one thou- 
sand electric lights to a distance of several hundred miles. Dr. Siemens 
had mentioned to him that the power of the Falls of Niagara might be 
transmitted electrically to a distance, and he need not point out the vast 
economy to be obtained by the use of such a fall as that of Niagara or 
the employment of waste coal at the pit’s mouth. In his evidence before 
the Select Committee referred to above he gave an estimate of the copper 
required to transmit 21,000 horse-power from Niagara to a distance of 
300 miles. 
In 1881 Thomson returned to the subject in his Presidential Address to 
Section A at York and said, ‘ High potential, as Siemens, I believe, first 
pointed out, is the essential for good dynamical economy in the electric 
transmission of power.’ He mentioned 80,000 volts as a suitable voltage. 
In a paper before the Section he developed the now well-known Kelvin 
Law of the most economical cross-section of the conductor. In 1890 the 
American promoters of the project for utilising the power of Niagara turned 
to Thomson for his advice, and he became a member of the Commission 
of Experts. He was throughout stubbornly opposed to the use of alter- 
nating currents ; he wrote, ‘ I have no doubt in my own mind but that the 
high-pressure direct-current system is greatly to be preferred to alternating 
currents. The fascinating character of the mathematical problems and 
experimental illustrations presented by the alternating-current system 
and the facilities which it presents for the distribution of electric light 
through sparsely populated districts have, I think, tended to lead astray 
even engineers, who ought to be insensible to everything except estimates 
of economy and utility.’ He was in a hopeless minority, however, in 
this view, and the Falls of Niagara were harnessed to two-phase alternators 
with an output of 3,500 kilowatts each. Kelvin was present at the meeting 
of the British Association held in this city in 1897, and shocked many people 
by saying that he looked forward to the time when the whole water of 
Lake Erie would find its way to the lower level of Lake Ontario through 
machinery ; ‘I do not hope,’ he said, ‘ that our children’s children will 
ever see the Niagara Cataract.’ Although he was apparently very much 
impressed with the success of the Niagara system, he was not converted 
