Insulators Once More, tests on Brooks and Lefferts insulators

Insulators Once More.

WITH evident reference to an article recently published in THE TELEGRAPHER, under the head of "Scientific Quackery," our official contemporary says: "It has been the custom in certain quarters to decry and underrate the value of the conductors and insulators employed by the Western Union Telegraph Company." In order to disprove our statement he gives the measurement of two wires in General STAGER'S division, between Chicago and Detroit. It will be remembered we said nothing about Gen. STAGER'S division, for the good reason that from personal observation we know very little about it. From what we have heard we think, however, that the wires there are in much better working condition than they are in the East. General STAGER uses BROOKS' insulators on his wires in the cities, where good insulation is far more essential than in the open country. We expressly said in our article, "We can speak from actual knowledge and. observation only, as far as the lines north of Washington are concerned." Why does he not give us tests from 145 Broadway, on some of the wires we referred to in our article, instead of going a thousand miles off to get a test of wires partially insulated with paraffine insulators?

Perhaps, however, we can explain the reason out-selves. On December 22d, 1867, Mr. C. F. VARLEY measured the insulation of 22 wires terminating at the office, 145 Broadway. "Weather wet," "Lines working badly." No. 12, South, gave the highest measurement, 115.500 ohms. This was insulated on the old BROOKS (not the improved). No. 20, which was not given in this test, was insulated with the same, and in all other tests given shows better than No. 12. The next in order were 14 wires insulated with the LEFFERTS, the highest of which gave 77.550 ohms. Then seven glass and bracket, the highest of which was 67.200 ohms, averaging about one twentieth of the insulation of the wires given in General STAGER'S division.

Now, we wish to call attention to the fact that, whenever any change is made in the insulation, it is to throw away those standing highest by Mr. VARLEY'S tests, and to substitute the kind which gave the worst results - the object being apparently to get the resistance of the insulators down to the lowest possible point. From the reports of the operators we should judge that their efforts were crowned with eminent success.

According to MOSES G. FARMER, who has made a large number of careful tests, the average resistance of the best glass insulators in use is not above nine megohms each, in a heavy and long continued rain, and he also says this is above the average value of three quarters of the insulators in use, in the middle and northern States. With 38 poles to the mile this would give a mileage insulation resistance of only 237.000 ohms. Our own tests have given results scarcely as good as those of Mr. FARMER. We think it would not be easy to find a wire on glass insulators, with 38 or 40 poles per mile, that will test over a megohm per mile when thoroughly wet by a long rain throughout the whole length. It would be a pretty heavy strain on the capacity of the insulators to accomplish such a result.