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had the zealous co…operation of the leading workmen themselves； and
the gratitude of all。 On the opening of the new and enlarged rooms in
1825； we find him delivering an admirable address； which was thought
worthy of republication； together with the reply of George
Sutherland； one of the workmen； in which Mr。 Neilson's exertions as
its founder and chief supporter were gratefully and forcibly
expressed。*
＇footnote。。。
Glasgow Mechanic's Magazine； vol。 iii。 p。 159。
。。。＇
It was during the period of his connection with the Glasgow Gas…works
that Mr。 Neilson directed his attention to the smelting of iron。 His
views in regard to the subject were at first somewhat crude； as
appears from a paper read by him before the Glasgow Philosophical
Society early in 1825。 It appears that in the course of the preceding
year his attention had been called to the subject by an iron…maker；
who asked him if he thought it possible to purify the air blown into
the blast furnaces； in like manner as carburetted hydrogen gas was
purified。 The ironmaster supposed that it was the presence of sulphur
in the air that caused blast…furnaces to work irregularly； and to
make bad iron in the summer months。 Mr。 Neilson was of opinion that
this was not the true cause； and he was rather disposed to think it
attributable to the want of a due proportion of oxygen in summer；
when the air was more rarefied； besides containing more aqueous
vapour than in winter。 He therefore thought the true remedy was in
some way or other to throw in a greater proportion of oxygen； and he
suggested that； in order to dry the air； it should be passed； on its
way to the furnace； through two long tunnels containing calcined
lime。 But further inquiry served to correct his views； and eventually
led him to the true theory of blasting。
Shortly after； his attention was directed by Mr。 James Ewing to a
defect in one of the Muirkirk blast…furnaces； situated about half a
mile distant from the blowing…engine； which was found not to work so
well as others which were situated close to it。 The circumstances of
the case led Mr。 Neilson to form the opinion that； as air increases
in volume according to temperature； if he were to heat it by passing
it through a red…hot vessel； its volume would be increased； according
to the well…known law； and the blast might thus be enabled to do more
duty in the distant furnace。 He proceeded to make a series of
experiments at the Gas…works； trying the effect of heated air on the
illuminating power of gas； by bringing up a stream of it in a tube so
as to surround the gas…burner。 He found that by this means the
combustion of the gas was rendered more intense； and its illuminating
power greatly increased。 He proceeded to try a similar experiment on
a common smith's fire； by blowing the fire with heated air； and the
effect was the same； the fire was much more brilliant； and
accompanied by an unusually intense degree of heat。
Having obtained such marked results by these small experiments； it
naturally occurred to him that a similar increase in intensity of
combustion and temperature would attend the application of the
process to the blast…furnace on a large scale； but being only a
gas…maker； he had the greatest difficulty in persuading any
ironmaster to permit him to make the necessary experiment's with
blast…furnaces actually at work。 Besides； his theory was altogether
at variance with the established practice； which was to supply air as
cold as possible； the prevailing idea being that the coldness of the
air in winter was the cause of the best iron being then produced。
Acting on these views； the efforts of the ironmasters had always been
directed to the cooling of the blast； and various expedients were
devised for the purpose。 Thus the regulator was painted white； as
being the coolest colour； the air was passed over cold water； and in
some cases the air pipes were even surrounded by ice； all with the
object of keeping the blast cold。 When； therefore； Mr。 Neilson
proposed entirely to reverse the process； and to employ hot instead
of cold blast； the incredulity of the ironmasters may well be
imagined。 What！ Neilson； a mere maker of gas； undertake to instruct
practical men in the manufacture of iron！ And to suppose that heated
air can be used for the purpose！ It was presumption in the extreme；
or at best the mere visionary idea of a person altogether
unacquainted with the subject！
At length； however； Mr。 Neilson succeeded in inducing Mr。 Charles
Macintosh of Crossbasket； and Mr。 Colin Dunlop of the Clyde Iron
Works； to allow him to make a trial of the hot air process。 In the
first imperfect attempts the air was heated to little more than 80
degrees Fahrenheit； yet the results were satisfactory； and the
scoriae from the furnace evidently contained less iron。 He was
therefore desirous of trying his plan upon a more extensive scale；
with the object； if possible； of thoroughly establishing the
soundness of his principle。 In this he was a good deal hampered even
by those ironmasters who were his friends； and had promised him the
requisite opportunities for making a fair trial of the new process。
They strongly objected to his making the necessary alterations in the
furnaces； and he seemed to be as far from a satisfactory experiment
as ever。 In one instance； where he had so far succeeded as to be
allowed to heat the blast…main； he asked permission to introduce
deflecting plates in the main or to put a bend in the pipe； so as to
bring the blast more closely against the heated sides of the pipe；
and also increase the area of heating surface； in order to raise the
temperature to a higher point； but this was refused； and it was said
that if even a bend were put in the pipe the furnace would stop
working。 These prejudices proved a serious difficulty in the way of
our inventor； and several more years passed before he was allowed to
put a bend in the blast…main。 After many years of perseverance； he
was； however； at length enabled to work out his plan into a definite
shape at the Clyde Iron Works； and its practical value was at once
admitted。 At the meeting of the Mechanical Engineers' Society held in
May； 1859； Mr。 Neilson explained that his invention consisted solely
in the principle of heating the blast between the engine and the
furnace； and was not associated with any particular construction of
the intermediate heating apparatus。 This； he said； was the cause of
its success； and in some respects it resembled the invention of his
countryman； James Watt； who； in connection with the steam…engine；
invented the plan of condensing the steam in a separate vessel； and
was successful in maintaining his invention by not limiting it to any
particular construction of the condenser。 On the same occasion he
took the opportunity of acknowledging the firmness with which the
English ironmasters had stood by him when attempts were made to
deprive him