14 Experiments for ascertaining [Jan., 
of steel, which in every case is greatly superior to iron in all the 
varied forms of resistances to strain to which it may be subjected. 
We have given this short abstract from a long series of recent 
experiments in anticipation of steel superseding iron in almost every 
case where strength 1s required. That the time is not far distant 
when this will be accomplished, we have every reason to believe, 
and assuming that the change will be of great national benefit, we 
shall hail with the liveliest satisfaction the disappearance of iron and 
the substitution of steel as a superior material for general purposes 
of construction. 
Ill. ON EXPERIMENTS FOR ASCERTAINING THE 
TEMPERATURE OF THE EARTH’S CRUST. 
By Epwarp Hutt, F.RS. 
THE question of the rate of increase of temperature of the Earth’s 
crust from the surface downwards is one which engaged the atten- 
tion of members of the British Association at the recent meeting in 
Dundee, and to the investigation of which, by actual experiment, 
the Association is likely to devote some portion of its funds. In 
anticipation of such operations, we venture to offer a few observations 
both as regards what has been done and what may be done and 
the mode of doing it, even at the risk of suggesting matters which 
have already occurred to the minds of those who are to carry out 
the experiments entrusted to them. It is desirable that whatever 
money and labour are to be devoted to this purpose should not 
be uselessly expended in the repetition of observations which have 
already been made with a degree of accuracy as great, perhaps, as the 
case admits of, but that they should be used in perfectly new and un- 
tried grounds, or, in other words, for the testing of hitherto unex- 
plored depths. Before entering, however, upon this branch of our 
subject, we shall prepare the way by bringing to the reader’s notice 
examples of what has already been done by previous investigators. 
Although the opinions of philosophers regarding the condition 
of the internal nucleus of the globe are widely different, all are 
probably agreed as regards an actual increase of temperature from 
the surface downwards to an unknown depth; and that this is the 
fact the evidence both of a theoretical and experimental character is 
probably conclusive. It is no argument against this view that we 
find strata, in their natural or unaltered state, which on stratigra- 
phical grounds we believe to have been at one time buried beneath 
newer strata to a depth of several thousand feet ; for assuming the 
increase of heat to be at an average rate of 1° Fahr. for every 60 
