Temistocle Calzecchi-Onesti's experiments with tubes of metal filings, as reported in "Il Nuovo Cimento" in 1884, led to the development of the first radio wave detector, the coherer, by Branly some years later.

This Branly showed by placing metal filings in a glass box or tube, and making them part of an ordinary electric circuit.

[10] 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.

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.

Another method of making the test was, by connecting the electrodes of a capillary electrometer to the two poles of a Daniell cell with a sulphate of cadmium solution.

The displacement of mercury which takes place when the cell is short-circuited, only takes place very slowly when an ebonite plate, covered with a sheet of copper of high resistance, is inserted between one of the poles of the cell, and the corresponding electrode of the electrometer; but when sparks are produced by a machine, the mercury is rapidly thrown into the capillary tube owing to the sudden diminution in the resistance of the plate.

[15] Branly found that, upon examination of the conditions necessary to produce the phenomena, the following data:[15] Summing up, he stated that in all these tests the use of ebonite plates covered with copper or mixtures of copper and tin was less satisfactory than the use of filings; with the plates he was unable to obtain the initial resistance of the body after the action of the spark or of the current, while with the tubes and filings the resistance could be brought back to its normal value by striking a few sharp blows on the support of the tube.

Branly is also commemorated by a technical High School (lycée) in Châtellerault, a commune in the Vienne department in the Poitou-Charentes region.