correspondent is entirely in error is assuming that there is. Let me suggest that if 'Investigator' really wishes to investigate, and is competent and willing to learn the exact facts, he can do so at this office, where there is no mystery of concealment, but, on the contrary, a strong desire to communicate facts to intelligent inquirers. Such a method of investigating must certainly be more satisfactory to one honestly seeking knowledge than that of first assuming an error as the basis of a question, and then demanding an explanation. "Yours very truly, "S. B. EATON, President." Viewed from the standpoint of over twenty-seven years later, the wisdom and necessity of answering anonymous newspaper letters of this kind might be deemed questionable, but it must be remembered that, although the Pearl Street station was working successfully, and Edison's comprehensive plans were abundantly vindicated, the enterprise was absolutely new and only just stepping on the very threshold of commercial exploitation. To enter in and possess the land required the confidence of capital and the general public. Hence it was necessary to maintain a constant vigilance to defeat the insidious attacks of carping critics and others who would attempt to injure the Edison system by misleading statements. It will be interesting to the modern electrician to note that when this pioneer station was started, and in fact for some little time afterward, there was not a single electrical instrument in the whole station--not a voltmeter or an ammeter! Nor was there a central switchboard! Each dynamo had its own individual control switch. The feeder connections were all at the front of the building, and the general voltage control apparatus was on the floor above. An automatic pressure indicator had been devised and put in connection with the main circuits. It consisted, generally speaking, of an electromagnet with relays connecting with a red and a blue lamp. When the electrical pressure was normal, neither lamp was lighted; but if the electromotive force rose above a predetermined amount by one or two volts, the red lamp lighted up, and the attendant at the hand-wheel of the field regulator inserted resistance in the field circuit, whereas, if the blue lamp lighted, resistance was cut out until the pressure was raised to normal. Later on this primitive indicator was supplanted by the "Bradley Bridge," a crude form of the "Howell" pressure indicators, which were subsequently used for many years in the Edison stations.