1864. | Physics. 161 
operation. Mr. Gore* has described a new gas-furnace, which possesses 
many advantages over those hitherto used. It would be difficult to 
rénder its construction intelligible without drawings; but the value of 
it may be understood when we say that the smallest size will melt half- 
a-pound of copper or six ounces of cast-iron in less than a quarter of 
an hour, at a cost of about,one halfpenny. The melted substances are 
perfectly accessible to be manipulated upon for a continuous and 
lengthened period of time, without contact with impurities or with the 
atmosphere, and without lowering their temperature sufficiently to cause 
them to solidify. Moreover, these advantages are secured by means 
of ordinary coal-gas and atmospheric air, without the use of a bellows 
or a lofty chimney, or of regenerators or valves requiring frequent 
attention. 
Execrriciry.—The passage of an electrical discharge through 
various gases and between electrodes of various metals, gives rise to 
different luminous phenomena. When this light is examined in the 
spectroscope, it has been found that each elementary gas or metal 
possesses certain well-marked characteristic lines, and it has generally 
been assumed :—1. That each substance has a set of lines peculiar to 
itself. 2. That those lines are not produced or modified by any mole- 
cular agent except heat. 3. That the spectrum of one substance is 
in nowise modified by the presence of another; in such cases both 
spectra co-existing independently, and are merely superposed. 4. That 
electricity does not make matter luminous directly, but only by heating 
it, so that the electric spectrum differs in nothing from that produced 
by heat of sufficient intensity. Dr. Robinson has examined these 
questions in a long and laborious investigation, and the result has been 
presented to the Royal Society, in a Paper “On the Spectra of Electric 
Light.” The opinion to which his results seem to point, is that the 
origin of the lines is to be referred to some yet undiscovered relation 
between matter in general and the transfer of electric action ; the places 
of the lines being invariably the same, but their brightness being 
_ modified according to circumstances. 
Since attention has been directed to the enormous variation in elec- 
tric conducting power, caused by the admixture of even minute quan- 
tities of metallic or other impurities in copper, it has become a question 
of some interest to determine the electric conducting power of all the 
pure metals. Professor Matthiessen + has continued his researches on 
this subject, and has lately determined the electrical relations of pure 
thallium. At the freezing point of water this metal has a conducting 
power equal to 9-16 (pure silver being 100), and its conducting power 
decreases between the freezing and boiling point, 51°420 per cent., 
which is a larger percentage decrement than that obtained for many 
other pure metals, namely, 29°307 per cent.{ The conducting power 
of pure iron was found to be, at 0? C= 16°81, with a percentage decre- 
ment for an increase of temperature to 100°C = 38:1. The conducting 
* «Chemical News,’ vol. viii. p. 2. 
+ ‘Philosophical Transactions,’ 1863. 
t ‘Philosophical Transactions,’ Part. I., 1862. 
VOL. I. M 
