FIRST REFORT— 1831. 
64 
tracing and pursuing them through all their consequences^ 
which led to several of his most brilliant discoveries. Of these 
analogies many were just and legitimate, and have stood the test 
of examination by the clearer light, since reflected upon them 
from the improved condition of science. But, in other cases, 
his analogies were fanciful and unfounded, and led him far astray 
from the path, which might have conducted him directly to 
truth. It is curious, however, as he himself observes, that in 
missing one thing, of which he was in search, he often found 
another of greater value. In such cases, his vigilance seldom 
failed to put him in full possession of the treasure upon which 
he had stumbled. Finding by experience, how much chance 
had to do with the success of his investigations, he resolved to 
multiply experiments, with the view of increasing the numerical 
probabilities of discovery. We find him confessing, on one 
occasion, that he “was led on, by a random expectation of some 
change or other taking place.” In other instances, he was in¬ 
fluenced by theoretical views of so flimsy a texture, that they 
were dispersed by the first appeal to experiment. “ These 
mistakes,” he observes, “it was in my power to have concealed; 
but I was determined to show how little mystery there is in the 
business of experimental philosophy; and withhow little sagacity, 
discoveries, which some persons are pleased to consider great 
and wonderful, have been made.” Candid acknowledgements 
of this kind were, however, turned against him by persons 
envious of his growing fame; and it was asserted that all his 
discoveries, when not the fruits of plagiarism, were “lucky 
guesses,” or owing to mere chance Such detractors, however, 
could not have been aware of the great amount of credit that 
is due to the philosopher, who at once perceives the value of a 
casual observation, or of an unexpected result; who discriminates 
what facts are trivial, and what are important; and selects the 
latter, to guide him through difficult and perplexed mazes of 
investigation. In the words of D’Alembert, “ Ces hazards ne 
sont que pour ceux qui jouent bien” 
The talents and qualifications which are here represented 
as having characterized the mind of Dr. Priestley, though not 
of the rarest kind, or of the highest dignity, were yet such as 
admirably adapted him for improving chemical science at the 
time when he lived. What was then wanted, was a wider field 
of observation;—an enlarged sphere of chemical phenomena;— 
an acquaintance with a far greater number of individual bodies 
* These charges, especially that of plagiarism, which had been unjustly ad¬ 
vanced by some friends of Dr. Higgins, were triumphantly repelled by Dr. Priest¬ 
ley, in a pamphlet entitled, “ Philosophical Empiricism,” published in 1775. 
