Blaise, meanwhile, was absorbed in scientific pursuits. To the acquisition of Latin and Greek was added the study of logic and physics; every moment of his time was occupied--and even during meals the work of study went on. Charmed with the progress his son made, and his apparent facility in learning, the father was blind to the ill-effects that such constant application had on his health: at the age of eighteen, Pascal began to droop; the indisposition he suffered was slight, and he did not permit it to interfere with his studies; but neglected, and indeed increased, it at last entirely disorganised his fragile being. From that hour he never passed a single day free from pain. Repose, taken at intervals, mitigated his sufferings; but when better he eagerly returned to study--and with study illness recurred.
His application was of the most arduous and intense description. At the age of nineteen he invented his arithmetical machine, considered one of the most wonderful discoveries yet put into practice. A machine capable of automatic combinations of numbers has always been a desideratum; and Pascal's was sufficiently well arranged to produce exact results--but it was very complex, expensive, and easily put out of order, and therefore of no general utility, though hailed by mathematicians as a most ingenious and successful invention. It cost him intense application, both for the mental combinations required, and the mechanical part of the execution:--his earnest and persevering study, and the great efforts of attention to which he put his brain, increased his ill health so much that he was obliged for a time to suspend his labours.
Soon after this, a question, involving very important consequences in physics, agitated the scientific world, and the position of the two Pascals was such, that their attention could not fail to be drawn to the consideration of it. The mechanical properties of the atmosphere had previously been inquired into by Galileo, who recognised in it the quality of weight. This philosopher, however, notwithstanding the wonderful sagacity which his numerous physical discoveries evince, failed to perceive that the weight of the atmosphere, combined with its fluidity and elasticity, opposed a definite force to any agent by which the removal of the atmosphere from any space was attempted. This resistance to the production of a vacuum had long been recognised, and was in fact expressed, but not accounted for, by the phrase, "nature's abhorrence of a vacuum." Whatever meaning he may have attached to it, Galileo retained this phrase, but limited its application, in order to embrace the phenomenon, then well known, that suction-pumps would not raise water more than about thirty-five feet high; and although "nature's abhorrence of a vacuum" raises the water thirty-five feet, to fill the space deserted by the air, which had been drawn out by the piston, yet above that height a vacuum still remained; which fact Galileo expressed by saying, that "thirty-five feet was the limit of nature's abhorrence of a vacuum."