To Professor E. Branly unquestionably belongs the honour of giving to science a new weapon in the shape of a tube containing metallic filings or powder rather loosely packed between metal plugs, and of showing that when the pressure on the powder was adjusted such a tube may be a conductor of very high resistance, but that the electrical conductivity is enormously increased if an electric spark is made in its neighbourhood. He also proved that the same effect occurred in the case of two slightly oxidised steel or copper wires laid across one another with light pressure, and that this loose or imperfect contact was extraordinarily sensitive to an electric spark, dropping in resistance from thousands of ohms to a few ohms when a spark was made many yards away. It is curious to notice how long some important researches take to become generally known. Branly's work did not attract much attention in England until 1892, when Dr. Dawson Turner described his own repetition of Branly's experiments with the metallic filings tube at a meeting of the British Association in Edinburgh. In the discussion which followed, Professor George Forbes made an important remark. He asked whether it was possible that the decrease in resistance could be brought about by Hertz waves.[29] This question shows that even in 1892 the idea that the effect of the spark on the Branly tube was really due to Hertzian waves was only just beginning to arise. The following year, however, Mr. W. B. Croft repeated Branly's experiment with copper filings before the Physical Society of London, and entitled his short Paper "Electric Radiation on Copper Filings."[30] He exhibited a tube containing copper filings loosely held between two copper plugs and joined in series with a galvanometer and cell. The effect of an electric spark at a distance, in causing increase of conductivity, was shown, and the return of the tube to its non-conducting state when tapped was also noticed. In the discussion which followed the reading of this Paper, Professor Minchin described the effects of electric radiation on his impulsion cells. He followed up this by reading a Paper to the Physical Society on November 24, 1893, on the action of Hertzian radiation on films containing metallic powders, and expressed the opinion that the change in resistance of the Branly tube was due to electric radiation.[31] Thus, at the end of 1893, a few physicists clearly recognised that a new means had been given to us for detecting those invisible ether waves, the chief properties of which Hertz had unravelled with surpassing skill six years before, by means of a detector consisting of a ring of wire having a small spark-gap in it.