JANUARY 21, 1904] 
NATURE 
7 
7 
first permanent deformations some grains only are 
deformed slightly, and as the stress augments more 
grains are deformed, and the deformation of the others 
increases. No definite dulling of the polished metal 
visible to the naked eye takes place, and the effects 
must be studied by means of the microscope. The 
polishing must also be done with the greatest care. 
The line of demarcation between the permanently 
strained and unstrained parts is even then always con- 
fused, and its exact position a little doubtful, but other- 
wise there is no difference between the testing of the 
two classes. In all cases the surface to be examined 
must be polished, for a scale of oxide has an elastic 
limit different from that of the metal underneath, and 
its indications are untrustworthy. 
Similar results are obtainable in tests of flexion, 
torsion, &c. 
By his experiments M. Frémont has proved that the 
Fic. 1 —The dark areas at the upper parts of the test pieces show 
where the metal has given way under compression. 
theoretical elastic limit is the mean charge per unit 
of section on which the real elastic limit is locally 
attained at a point of the piece tried. It is not the 
elastic limit of the metal, but of the particular piece 
NO. 1786, VOL. 69] 
of metal under the special conditions employed. Its 
value depends on care in adjustment, &c. k 
The proportional elastic limit is still more fortuitous. 
Owing to compensating errors the line showing the 
relation between stress and strain may continue to be 
fairly straight even above the theoretical limit. 
The apparent limit is the mean charge per unit of 
section when the real elastic limit is reached in all 
regions where it had not 
previously been reached. It 
is nearer the real limit but 
is not identical with it, be- 
cause the charge is un- 
equally distributed between 
the parts that have been 
previously hardened and 
those that are not yet 
hardened. 
When the appearance of 
the lines of Ltiders, which 
are now seen to be portions 
of metal which have given 
way, does not precede the 
continuous sheet, the theo- 
retical limit and the 
apparent limit will coincide 
with the real limit. Gener- 
ally, however, the lines 
come first and then the 
various limits will not co- 
incide. 
The nature of the metal 
has also an effect, for in 
annealed steel the two 
limits are nearer than in 
hardened and tempered 
steel. 
To sum up, M. Frémont 
claims with much force 
that there is only one elastic 
limit of a metal, the ‘‘ real 
elastic limit,’? as  deter- 
mined by the method he 
indicates. The real limit 
alone has the characters of 
ay physical Constant The Fic. 2.—The dark areas on the 
other so-called limits de- test pieces correspond to the 
pend on the appearance of noxious of the metal ch 
discontinuous deformations, BAO orca ES 
the presence of which is 
almost inevitable in practice, although their cause is 
purely accidental. Re Kea Re 
PREHISTORIC STUDIES IN AUSTRIA. 
“pists concluding part of the first volume of reports of 
the Prehistoric Committee of the Vienna 
Academy of Sciences has recently been published.” In 
former parts accounts have been given by Dr. Szom- 
bathy of excavations in the well-known cemetery at 
Hallstatt, of tumuli at Gemeinlebarn and Langenle- 
barn, and of the cemetery at Idria. Dr. Franz Heger 
has also treated of work carried on at Hallstatt in 1877 
and 1878, as well as of various researches in Hungary 
and Lower Austria, while Dr. Moriz Hoernes and 
others have communicated valuable reports. 
The part now issued contains two reports. The 
first, by Julius Teutsch, relates to some late Neolithic 
settlements with painted pottery in the valley of the 
Alt or Aluta, in the neighbourhood of Kronstadt, in 
Transylvania. A remarkable feature in one of the de- 
1 “ Mittheilungen der Prahistorischen Commission der Kais. Akademie 
der Wissenschaften.” 1 Band. (Vienna: Carl Gerold’s Sohn, 1903.) 
