part of an ordinary electric circuit. According to the common explanation, when electric waves are set up in the neighborhood of this circuit, electromotive forces are generated in it which appear to bring the filings more closely together, that is, to cohere, and thus their electrical resistance decreases, from which cause this piece of apparatus was termed by Sir Oliver Lodge a coherer. Hence the receiving instrument, which may be a telegraph relay, that normally would not indicate any sign of current from the small battery, can be operated when electric oscillations are set up. Prof. Branly further found that when the filings had once cohered they retained their low resistance until shaken apart, for instance, by tapping on the tube. In On the Changes in Resistance of Bodies under Different Electrical Conditions, he described how the electrical circuit was made by means of two narrow strips of copper parallel to the short sides of the rectangular plate, and forming good contact with it by means of screws. When the two copper strips were raised the plate was cut out of the circuit. He also used as conductors fine metallic filings, which he sometimes mixed with insulating liquids. The filings were placed in a tube of glass or ebonite, and were held between two metal plates. When the electrical circuit, consisting of a Daniell cell, a galvanometer of high resistance, and the metallic conductor, consisting of the ebonite plate, and the sheet of copper, or of the tube containing the filings, was completed, only a very small current flowed; but there was a sudden diminution of the resistance which was proved by a large deviation of the galvanometer needle when one or more electric discharges were produced in the neighbourhood of the circuit. In order to produce these discharges a small Wimshurst influence machine may be used, with or without a condenser, or a Ruhmkorff coil. The action of the electrical discharge diminishes as the distance increases; but he observed it easily, and without taking any special precautions, at a distance of several yards. By using a Wheatstone bridge, he observed this action at a distance of 20 yards, although the machine producing the sparks was working in a room separated from the galvanometer and the bridge by three large apartments, and the noise of the sparks was not audible. The changes of resistance were considerable with the conductors described.