tubes of colored glass, it would be easy to telegraph by night, as they could be extinguished and relighted rapidly from the deck.

"For lighthouse purposes considerable amplitude can be given to the light. I also saw a lamp so arranged, in a thick glass globe, that it could be immersed to considerable depths without being extinguished by any movement. This lamp has already been used in the taking of fish, which were attracted towards the light.

"The above slight description will suffice to show to what a variety of applications this discovery can be put. The communication which I have had the honor of laying before the Academy is founded upon no illusion; a lamp was, to my astonishment, lit in the hollow of my hand, and remained alight after I had put it in my pocket with my handkerchief over it."

In looking the matter up in the Comptes Rendus, or minutes of the French Academy, I find that the communication of M. Jobart was received at the meeting held March 1st, 1858, and was referred to M. Becquerel. At the meeting of April 5th, M. Becquerel reported that he did not find anything sufficiently definite to warrant the Academy to express an opinion as to the importance of this discovery. "All that was desirable at present was fuller information." At the meeting of April 19th M. Jobart responds to this request by stating that "he could not give more precise details without exposing the author to see another, profit by his discovery.”

Familiar as is the fact that history repeats itself, we cannot but be struck by the many points of resemblance between the above and what we read in the newspapers of to-day, concerning the wonderful doings at Menlo Park, and must hope that Mr. Edison's inventions will escape that permanent obscuration which seems to have finally shrouded M. de Changy's.

It would appear as if this brilliant and complete success described by M. Jobart as achieved by M. de Changy in Paris, in February, 1858, was very rapidly followed up in this country, for I learn from a letter in the Salem Observer of Nov. 2, 1868, that Mr. Moses G. Farmer, in Salem, lit his parlor every

evening during July of 1859 with electric lamps operated on a like principle.

It is true that nineteen years have not sufficed to render this admirable arrangement successful in practice, but what is that to the prophetic mind which, foreseeing what is to happen in the "near future," naturally overleaps distinctions between past and future, theory and practice.

For us, however, who only know the past and the present, it may be well to look a little closer at the means actually used, and the results obtained, in these and other experiments.

In the first place, let me show you what this light by incandescence actually is.

There is a coil of platinum wire, through which I pass the current from a battery. It grows first red, then yellow, then white, and now it gives out a beautiful soft and steady light; but we must be cautious; if I allow the current to become a little stronger, the wire fuses and drops asunder, and our experiment is at an end.

It is, as I understand, just here that Mr. Edison has made his much announced but carefully concealed invention. He has devised some simple and ingenious arrangement by which the solid conductor can be brought up to the highest point of incandescence, without risk of fusion.

True, this achievement was claimed for M. de Changy, and seems to be implied in Mr. Farmer's description; but somehow, as with the famous perpetual motion machine, the little screw which makes it all go" does not appear to have been forthcoming in either case; and in this present year of 1878 we still look to the future,' near or remote, for the "practical success so confidently announced nineteen or twenty years ago.

The first electric lamp operating by incandescence of which we have any actual record seems to be that invented by the American, Starr, a patent for which was taken out in England by his agent, King, in 1845, and which has thus come to be known as the King lamp. This lamp has been modified in details until it has reached the form shown in Fig. 3, known as the King lamp.

This apparatus consists of a glass vessel provided with a metal cap and packing box below, by means of which it can be closed air-tight.

A connector at K allows of the exhaustion of air from the interior, and the filling of the interior with any inactive gas.

Two upright metallic conductors, connected respectively with the two poles of the electric circuit, pass up through this glass vessel and at their upper ends support, as shown, two or more rods of carbon or other conductors. The electric connection with these rods is made from C by means of the lever I, which communicates first with the longest rod, F, and when that is burned up, falls upon the next longest, and so on. The light is produced by the rod of carbon heated white hot by the

current.

Various slight modifications of this lamp have been made and elaborately experimented with; but they all show the same essential characteristics. The first of these, is, that as long as any oxygen remains in the vessel, the carbon rods consume rapidly, the first one generally lasting only twenty minutes. The second carbon will, however, last two hours if the light does not exceed forty burners; but even when all active gas has been removed, the carbon suffers a sort of vaporization.

The second characteristic of these incandescent lamps, is, .that with the same current, they develop much less light than is obtained from the electric arc. Thus, a battery of 48 elements, with a Serrin lamp, gave an electric arc equal to 100 burners; but with one of these lamps, gave a light equal only to 80 burners, and when divided between three lamps, gave only the light of 10 burners each.

The third characteristic is the manner in which the light-producing power of the current diminishes, as it is distributed between a number of lamps. Thus, the current from a given battery, acting on one lamp, produced a light between 4 and 5 burners; on two lamps, a light 11⁄2 burners each; on three lamps, one-third to two-thirds of a burner each. From another battery, the current on a single lamp gave a light of II to 12 burners; with two lamps, one-half burner each; and on three lamps, one-ninth of a burner each.

In another case a given battery with one lamp gave the light of 9 burners; with two lamps, 21⁄2 burners; and with three lamps, one-third of a burner each. Another battery with one lamp gave a light of 65 burners; with two lamps, 71⁄2 burners; with three lamps, 1 burners; with four lamps, three-fourths of a burner; and with five lamps, one-half burner each.

In this connection it is curious to notice that the latest accounts from Mr. Edison show that he gets a light equal to about 48 candles, or three argand gas burners, per horse power with his new device, and with similar machines for producing the electric current and the electric arc, from 1,000 to 2,000 candles per horse power; thus showing remarkable agreement with these earlier experiments as to the loss of effect resulting from the subdivision of the light.

Another modification of this Starr, or King lamp, is found in that which has been recently exhibited in New York as the Sawyer-Mann lamp.

This differs from the former apparatus in no important feature except that the interior of the vessel is said to be filled with pure nitrogen at the ordinary pressure. The carbon rods are said not to waste away in these lamps. Without knowing anything positively on the subject, my opinion is that this is simply because they have not been subjected to strong currents, but have only been heated to the extent of yielding the light of one or two burners. Under these circumstances, the carbons of the King lamp will last a long time, but on the other hand, the light so obtained is not economical, as we see above.

When exhibited in New York recently, we understood that five lamps only were operated by a magneto machine of Arnoux & Hochhausen, driven by a three-horse power steam engine, said to be developing only one and one-half horse power.

It is certain that none of these lamps have yet demonstrated anything like such practical success as can enable us to see that they can take the place of gas in ordinary illumination. They have, of course, many advantages in certain respects over the electric arc, but these are combined with compensat