Robin Lyth had chosen well his place for meeting Mary. The lane (of which he knew every yard as well as he knew the rocks themselves) was deep and winding, and fringed with bushes, so that an active and keen-eyed man might leap into thicket almost before there was a fair chance of shooting him. He knew well enough that he might trust Mary; but he never could be sure that the bold “coast-riders,” despairing by this time of catching him at sea, and longing for the weight of gold put upon his head, might not be setting privy snares to catch him in his walks abroad. They had done so when they pursued him up the Dike; and though he was inclined to doubt the strict legality of that proceeding, he could not see his way to a fair discussion of it, in case of their putting a bullet through him. And this consideration made him careful.

The brother and sister went on well by the foot-path over the uplands of the farm, and crossing the neck of the Flamburn peninsula, tripped away merrily northward. The wheat looked healthy, and the barley also, and a four-acre patch of potatoes smelled sweetly (for the breeze of them was pleasant in their wholesome days), and Willie, having overworked his brain, according to his own account of it, strode along loftily before his sister, casting over his shoulder an eddy of some large ideas with which he had been visited before she interrupted him. But as nothing ever came of them, they need not here be stated. From a practical point of view, however, as they both had to live upon the profits of the farm, it pleased them to observe what a difference there was when they had surmounted the chine and began to descend toward the north upon other people's land. Here all was damp and cold and slow; and chalk looked slimy instead of being clean; and shadowy places had an oozy cast; and trees (wherever they could stand) were facing the east with wrinkled visage, and the west with wiry beards. Willie (who had, among other great inventions, a scheme for improvement of the climate) was reminded at once of all the things he meant to do in that way; and making, as he always did, a great point of getting observations first—a point whereon he stuck fast mainly—without any time for delay he applied himself to a rapid study of the subject. He found some things just like other things which he had seen in Scotland, yet differing so as to prove, more clearly than even their resemblance did, the value of his discovery.

“Look!” he cried; “can anything be clearer? The cause of all these evils is not (as an ignorant person might suppose) the want of sunshine, or too much wet, but an inadequate movement of the air—”

“Why, I thought it was always blowing up here. The very last time I came, my bonnet strings were split.”

“You do not understand me; you never do. When I say inadequate, I mean, of course, incorrect, inaccurate, unequable. Now the air is a fluid; you may stare as you like, Mary, but the air has been proved to be a fluid. Very well; no fluid in large bodies moves with an equal velocity throughout. Part of it is rapid and part quite stagnant. The stagnant places of the air produce this green scum, this mossy, unwholesome, and injurious stuff; while the overrapid motion causes this iron appearance, this hard surface, and general sterility. By the simplest of simple contrivances, I make this evil its own remedy. An equable impulse given to the air produces an adequate uniform flow, preventing stagnation in one place, and excessive vehemence in another. And the beauty of it is that by my new invention I make the air itself correct and regulate its own inequalities.”

“How clever you are, to be sure!” exclaimed Mary, wondering that her father could not see it. “Oh, Willie, you will make your fortune by it! However do you do it?”

“The simplicity of it is such that even you can understand it. All great discoveries are simple. I fix in a prominent situation a large and vertically revolving fan, of a light and vibrating substance. The movement of the air causes this to rotate by the mere force of the impact. The rotation and the vibration of the fan convert an irregular impulse into a steady and equable undulation; and such is the elasticity of the fluid called, in popular language, 'the air,' that for miles around the rotation of this fan regulates the circulation, modifies extremes, annihilates sterility, and makes it quite impossible for moss and green scum and all this sour growth to live. Even you can see, Mary, how beautiful it is.”

“Yes, that I can,” she answered, simply, as they turned the corner upon a large windmill, with arms revolving merrily; “but, Willie dear, would not Farmer Topping's mill, perpetually going as it is, answer the same purpose? And yet the moss seems to be as thick as ever here, and the ground as naked.”

“Tush!” cried Willie. “Stuff and nonsense! When will you girls understand? Good-by! I will throw away no more time on you.”

Without stopping to finish his sentence he was off and out of sight both of the mill and Mary, before the poor girl, who had not the least intention of offending him, could even beg his pardon, or say how much she wanted him; for she had not dared as yet to tell him what was the purpose of her walk, his nature being such that no one, not even his own mother, could tell what conclusion he might come to upon any practical question. He might rush off at once to put the revenue men on the smuggler's track, or he might stop his sister from going, or he might (in the absence of his father) order a feast to be prepared, and fetch the outlaw to be his guest. So Mary had resolved not to tell him until the last moment, when he could do none of these things.