266 British Association for the Advancement of Science. 
ed if beaten red hot and very slowly cooled, which would make the 
metal softer, and the grain more uniform, and they might afterwards 
be hardened at the poles to produce the maximum effect. He con- 
sidered this result of much importance, as it will enable us to con- 
struct compound magnets for magneto-electrical machines with great 
facility, and at a very nine expense, as any number can be cast 
from one timber pattern.” 
“¢ Mr. Holden said, that he had bestowed much time and attention 
on the construction of magnets. He preferred steel tempered blue, 
or to spring temper, and was on the whole, inclined'to doubt the 
value of the material proposed. He knew that cast iron was capa- 
ble of receiving strongly the magnetic influence, and bars of cast 
iron, as long as they retained their upright position, were found to 
possess polarity in a very high degree ; but he doubted whether, if 
they were removed from their upright positions, they would long 
retain their polarity to any considerable extent.” 
“Mr. Snow Harris observed, that from many trials and much ex- 
perience, he was convinced that hardened steel wire, just as it is to 
be had in the shops, without any further working it, or putting it 
into the fire, or altering its temper, was the best material for con- 
structing small needles, intended to retain their magnetism perma- 
nently ; and this latter consideration was of the utmost consequence 
when constructing needles for philosophic research, as, for instance, 
upon the magnetic intensity at various places, since the slightest 
alteration of power, in that case, would most materially and injuri- 
ously affect the result.” 
Mr. Scoresby preferred evenly tempered steel such as watch 
springs or ladies’ busks. 
~ Prof. Henry had tried cast iron and found it did not retain its 
magnetic power. 
Tides.—* By a fortunate circumstance, the preservation of a reg- 
ister of the tides, kept for a short time during the 13th century, at 
London Bridge, by an abbot of St. Albans, John Wallingford, and 
which register had been preserved in the British Museum, it had 
had been clearly shown that the establishment for the port of London 
varied since that time by a quantity extending to between two and 
three hours: the cause of this could be as yet merely conjectured.” 
Jron.—On the use of Anthracite coal by the combination of 
heated air to the purpose of smelting tron ore.—‘‘ The reduction of 
the quantity of fuel expended to less than a third of that before re- 
