mechanical value about equal to that of steel of 35 tons per square inch tensile strength.

Mierzinski: Kamarsch (Dingler 172, 55) obtains the following results as the strength of aluminium wire:

Deville: A very curious property, which aluminium shows the more the purer it is, is its excessive sonorousness, so that a bar of it suspended by a fine wire and struck sounds like a crystal bell. M. Lissajous, who with me observed this property, has taken advantage of it to construct tuning forks of aluminium, which vibrate very well. I also tried to cast a bell, which has been sent to the Royal Institution at London at the request of my friend Rev. J. Barlow, vice-president and secretary of the institution. This bell, cast on a model not well adapted to the qualities of the metal, gives a sharp sound of considerable intensity, but which is not prolonged, as if the clapper or support hindered the sound, which, thus hindered, becomes far from agreeable. The sound produced by the ingots is, on the contrary, very pure and prolonged.

In the experiments made in Mr. Faraday's laboratory, this celebrated physicist has remarked that the sound produced by an ingot of aluminium is not simple. One can distinguish, by turning the vibrating ingot, two sounds very near together and succeeding each other rapidly, according as one or the other face of the ingot faces the observer.

Watts: Aluminium is highly sonorous, but a bell cast of it gave a sound like a cracked pot.

DENSITY.

Deville: The density of aluminium is 2.56; by rolling this is considerably increased, so as to become 2.67, indicating a considerable approaching of the molecules to each other; which may explain the differences existing in its properties after being annealed or worked. Heated to 100° and cooled, it changes very little, for its specific gravity is still 2.65. The following table compares it with the other metals:

Since the metal has been in commerce it has been sold at a high price; at present (1859) it can be bought in large quantities at 300 fr. per kilo; it is, therefore, much dearer than silver. But, because of the difference in their densities, for equal volumes of aluminium and silver, the value of the former must be divided by 4 in order to compare them; making a volume of aluminium much cheaper than an equal volume of silver, while, besides, it is much stronger. So, to-day, Al may be considered as costing 75 fr. to Ag 220 fr.

Mallet: The specific gravity of absolutely pure aluminium was carefully determined at 4° C., and the mean of three closely agreeing observations gave 2.583.

FUSIBILITY.

Deville: Aluminium melts at a temperature higher than that of zinc, lower than that of silver, but approaching nearer to that of zinc than silver. It is, therefore, quite a fusible metal.

Mallet: It seems that pure aluminium is a little less fusible than the commercial metal.

Mierzinski: The melting point of aluminium can be taken as about 700° C.

6*

FIXITY.

Deville: Aluminium is absolutely fixed, and loses no part of its weight when it is violently heated in a forge fire in a carbon crucible.

Watts: Aluminium heated in a closed vessel does not exhibit the slightest tendency to volatilize. Fremy: Aluminium is fixed at all temperatures.

ELECTRIC CONDUCTIVITY.

Deville: Aluminium conducts electricity with great facility, so that it may be considered as one of the best conductors known, and perhaps equal to silver. I found by Wheatstone's Bridge that it conducts eight times better than iron. M. Buff has arrived at results evidently different from mine because we have not taken the same ground of comparison. The difference is due, without doubt, to the metal which he employed containing, as is easily found in many specimens, a little cryolite and fusible materials, the density of which is near that of the metal, and which were employed in producing it. The complete separation of the metal and flux is a difficult mechanical operation, but which is altogether avoided by using a volatile flux. This is a condition which must be submitted to in order to get the metal absolutely pure.

'Jahresb. der Chemie,' 1881, p. 94: Aluminium

thus compares with copper and magnesium in electric conductivity:

After Al come red brass, Cd, yellow brass, Fe, Zn, Pb, Ag, Sb, Bi, in the order given.

Fremy: The electric conductivity of aluminium is 51.5, copper being 100; or 33.74, silver being

100.

THERMAL CONDUCTIVITY.

Deville: It is generally admitted that conductivity for heat and electricity correspond exactly in the different metals. A very simple experiment made by Mr. Faraday in his laboratory seems to place aluminium very high among metallic conductors. He found that it conducted heat better than silver or copper.

Watts: Aluminium conducts heat better than silver.

'Jahresb. der Chemie,' 1881, p. 94: Aluminium has the following conductivity for heat:

After Al come red brass, Cd, yellow brass, Fe,

Zn, Pb, Ag, Sb, Bi in the order given.