COUNCIL FOR 1871 . 
19 
ill-reasoning theologians, who sometimes appeared to forget 
that they were not endowed with “ supernatural knowledge of 
the mysteries of nature.” 
One of the subjects to which Mr. Harcourt directed his 
attention with success was the effect of heat on inorganic com¬ 
pounds. With a view to extensive experiments on the effects 
of high heats in a manageable form, he began the construction 
of a furnace for burning hydrogen gas under great pressure ; 
and by the aid of Sir William Fairbairn and the late Mr. 
Bryan Donkin, this furnace was provided with pressure-guages 
and became a safe and manageable instrument. It was em¬ 
ployed for many years in the processes of fusion, required for 
the production of various kinds of glass for optical uses. 
Following similar ideas he assisted as a Member of a Com¬ 
mittee of the British Association in the examination of furnace- 
slags, on which the Report was presented by Dr. Percy. As 
early as in 1834, another train of researches on the same 
general subject was set on foot by Mr. Harcourt when he made 
arrangements for trying the effects of long-continued heat on 
rooks and minerals. For this purpose the furnaces of Low 
Moor, in Yorkshire, were employed by placing under them a 
large and varied series of rocks and minerals and artificial 
mixtures selected and weighed to represent various natural 
crystals interesting to geologists in connection with metalli¬ 
ferous veins and metamorphic rocks. The furnaces being usually 
kept in action for several years, it was expected that the long- 
continued and moderate heat would be sufficient to fuse some 
metals and probably cause new combination of oxides, silicates, 
or sulphides. 
These operations gave indeed such results ; and though con¬ 
trary to expectation, the direct influence of high temperatme 
was found to be too great, the conglutination of sand to 
quartzite, the formation of iron veins, the occurrence of cavities 
lined with a web-like silicate, and what was almost a chaos of 
changes and displacements showed the power of the agencies 
employed. It is much to be desired that those curious expe¬ 
riments should be repeated with precautions which are suggested 
by those on record, 
