Gunnery, sir, is a science--we have our own disparts and our lines of sight--our windage, and our parabolas, and projectile forces--and our point blank, and our reduction of powder upon a graduated scale.

Now, sir, there's no excuse for a gunner not being a navigator; for knowing his duty as a gunner, he has the same mathematical tools to work with." Upon this principle, Mr Tallboys had added John Hamilton Moore to his library, and had advanced about as far into navigation as he had in gunnery, that is, to the threshold, where he stuck fast, with all his mathematical tools, which he did not know how to use.

To do him justice, he studied for two or three hours every day, and it was not his fault if he did not advance--but his head was confused with technical terms; he mixed all up together, and disparts, sines and cosines, parabolas, tangents, windage, seconds, lines of sight, logarithms, projectiles, and traverse sailing, quadrature, and Gunter's scales, were all crowded together, in a brain which had not capacity to receive the rule of three.

"Too much learning," said Festus to the apostle, "hath made thee mad." Mr Tallboys had not wit enough to go mad, but his learning lay like lead upon his brain: the more he read, the less he understood, at the same time that he became more satisfied with his supposed acquirements, and could not speak but in "mathematical parables".

"I understand, Mr Easy," said the gunner to him one day, after they had sailed for Malta, "that you have entered into the science of navigation--at your age it was high time." "Yes," replied Jack, "I can raise a perpendicular, at all events, and box the compass." "Yes, but you have not yet arrived at the dispart of the compass." "Not come to that yet," replied Jack.
"Are you aware that a ship sailing describes a parabola round the globe ?" "Not come to that yet," replied Jack.
"And that any propelled body striking against another flies off at a tangent ?" "Very likely," replied Jack; "that is a 'sine' that he don't like it." "You have not yet entered into 'acute' trigonometry ?" "Not come to that yet," replied Jack.
"That will require very sharp attention." "I should think so," replied Jack.
"You will then find out how your parallels of longitude and latitude meet." "Two parallel lines, if continued to infinity will never meet," replied Jack.
"I beg your pardon," said the gunner.
"I beg yours," said Jack.
Whereupon Mr Tallboys brought up a small map of the world, and showed Jack that all the parallels of latitude met at a point at the top and the bottom.
"Parallel lines never meet," replied Jack, producing Hamilton Moore.
Whereupon Jack and the gunner argued the point, until it was agreed to refer the case to Mr Jolliffe, who asserted, with a smile, "That those lines were parallels, and not parallels." As both were right, both were satisfied.