Brooks Paraffine Insulator

The Brooks Paraffine Insulator.

EARLY last year is was announced that Monsieur Vicomte DE VOUGY, Director General of the Telegraph Lines of France, had appointed a commission of electricians to decide upon a style and material of an insulator for Telegraph lines under his charge. This commission was composed of eminent electricians, among whom were Monsieurs GANGANI, GAVARRET, DU MONCEL, and others, whose names are familiar to all readers of works upon electrical science. The most approved insulators of the different countries in Europe were procured and tested in the open air, exposed to the weather. Among others presented for trial was the BROOKS Paraffine Insulator. After a trial of three months an order was given to Mr. BROOKS on October 1, 1867, for a sufficient number to enable the commission to make a practical test of their value. The result of this examination and test was made known through the columns of the Semaine Financiere, of January 24th, and La Union, of February 4th, stating that the BROOKS Insulator had proved far superior to all its competitors.

Telegraphers in England hearing of the success of this insulator, sent to Philadelphia for samples to test in comparison with their won amid the fogs and mists of London.

The table of results received from them, and published on page 341 of the last volume of THE TELEGRAPHER, shows that the merits of this insulator are not lost by a change of climate, or a transfer to hands in no wise interested in their development or exhibition.

A series of tests of insulators was made at Philadelphia, on the 22d of April, 1868, which fully confirmed the results of the experiments in the August number of the Journal of the Franklin Institute, whose editor was present on the occasion.

"The testing instruments employed were a set of resistance coils, made at the Silvertown works, and a RUHMKORFF galvanometer of admirable construction, whose delicacy was such that the contact of one finger with the brass binding screw at one terminal, while the finger of one hand rested on the copper wire at the other terminal, deflected the needle several degrees. The results are reduced to ohmads of resistance, to make them comparable with the Silvertown experiments, in which a far more sensitive galvanometer was employed and a more powerful battery.

"The constant of the galvanometer was first determined by passing the current of one of the sulphate of mercury cells, described by Mr. CHESTER, p. 257 of our last volume,* through a resistance of 10,000 units or ohmads, and the instrument thus gave an actual constant for one cell of 6,160*, or for the entire battery of 151 cells afterwards employed, of 930,160*.

"One pole of the battery being then connected with 83 BROOKS insulators, and the other through the galvanometer to the earth, a deflection of 8 deg was observed, giving for each insulator a deflection of 8/88 = 1/11 of a degree which represented a resistance, under the condition described above, of 102,317,600,000 ohmads.

"At the same date a trial was also made with 22 earthenware insulators, charged with paraffine by the same method as for the other insulators. The deflection in this case was 17 deg or 17/22 per insulator, which being reduced as before, gives 12,037,365,902 ohmads.

"There was then a trial immediately made with 22 glass and bracket insulators, the kind generally employed in this country. The deflection here measured was 7,852 deg, or 356-10/11 per insulator, showing a resistance in ohmads of 2,605,000.

"The atmospheric conditions under which these experiments were made were as follows: It had rained steadily on the 20th and 21st until evening, when a fog formed and continued until 8 A. M. of the 22d, when the deflections were greatest, and were measured as before stated.

"The Silvertown tests, on March 31, the time of greatest deflection, reduced to ohmads, stand as follows:

"Several points here are worth of remark. First, the English tests give a higher actual resistance for the BROOKS insulator than those made here. This is undoubtedly due to a better state of the weather. Such a favorable condition for putting to test the efficiency of insulators, as was furnished on April 22d, is, fortunately for the Telegraph companies, not often met with. Again, we see that the various English insulators tested were ahead of our usual glass and bracket, while these in their turn were left each further in the rear by the BROOKS apparatus.

"The constant of this galvanometer, made by RHUMKORFF, is, as we have already seen, 6,160 deg, with a single cell through 10,000 ohmads, while that of Prof. THOMPSON, used in the Silvertown tests, has a constant of 334 deg through 1,000,000 ohmads, or 100 times the resistance, thus showing that the delicacy of the English instrument was five times as great as the French.

"There is indeed no question that in all such matters, if connected with the application of scientific principles and accurate measurements to the practical working of telegraphic lines, the English are decidedly in advance of all other nations. On the other hand, there are a vast number of ingenious contrivances and simple ways of securing good results in constant use here, which are unknown abroad."

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* Also, page 257 of the last volume of THE TELEGRAPHER.