22 
DR. A. -MATTHIESSEN AND M. VON BOSE ON THE INFLUENCE OF 
The formuloD deduced from the observations, and from which the conducting powers 
were calculated, were — 
Forfii’stbar X = 3-7619+0-011614?^+0-0006598^=^+0-000002994^". 
For second bar to 2 9 ’4 . . X=20T62 — 0‘055338^+0’001085^^ 
For second bar from 29-4 to 100 X=20-014-0-029569^+0*00009390^^+0-000010635^^. 
Fortliu-dbar X=5-5752 + 0-019274!5+0-0013235f +0'000003088f. 
Fi’om the above Table we learn that tellurium behaves in a very diiferent manner 
H’om the other metals ; for it will be seen how very much the conducting power decreases 
after it has been heated to 100° for some days, and how different is the time required 
before the conducting power of the different bars becomes constant, or, in other words, 
until the heating of the bars to 100° causes no further permanent alteration in the 
conducting power. Bar I. required 13 days ; bar II. 32 ; bar III. 33. The first observed 
conducting power being taken equal to 100, bar I. is reduced to 4, bar II. to 19’6, and 
bar III. to 6. If we noAV look at the determinations of the conducting power at different 
temperatm*es of the three bars, we are struck at the great want of concordance in the 
results. With the fii’st series we observe that the conducting power increases rapidly as 
the temperature rises ; with the second it decreases with the rise of temperature to 
29°’4, from which point it increases rapidly, as udth bar I. ; the third behaves as the 
first. 
Bar I. showed no apparent difference in crystalline structure after being heated ; it 
was thought very probable that the crystalline structure might have been altered by 
heating, and thus caused the enormous change in conducting power. The three bars, 
when first heated, behaved as metal to 70° or 80°, that is to say, they lost in conducting 
power up to that temperature, where it then began to increase. The temperature of 
this tm’ning-point became lower after each day’s heating, until, as in bars I. and II., it 
is below the lowest temperature at which observations were made. 
The behaviour, therefore, of tellurium is intermediate between that of the metal and 
that of the metalloid; for, according to Hittoep*, selenium increases rapidly in conduct- 
ing power with the temperature. Graphite and gas-coke f behave in the same manner; 
and Becquekel J found that gases when heated conduct better than when cold. From 
these facts we learn another marked difference in the physical properties of the metals 
and metalloids, viz. that the metals lose in conducting power with an increase of tempera- 
ture, whereas under the same circumstances the metalloids gain. 
In order to be better able to compare the results obtained with the pure metals, we 
give the following Tables. Table XIV. contains all the formulae deduced from the 
observations by the method of least squares, with the conducting power of each metal 
taken =100 at 0°; Table XV. the mean of the formulae found for each metal. 
* PoGGEiroOEiT’s ‘ A Tin 3.1 en,’ vol. Ixsxvi. p. 214. 
f Philosophical Transactions, 1858, p. 386. 
f Ann. de Chim. et de Phys. (iii.) vol. xxxix. p. 388. 
