Where Gravesend merges into Northfleet—where the spicy odors of chemical-fertilizing works mingle with the dry dust of the cement manufactories which throw their tall chimneys into an ever-gray sky—there stands a house known as the Signal House. Why it is so called no one knows and very few care to inquire. It is presumably a square house of the Jacobean period—presumably because it is so hidden by trees, so wrapped in grimy ivy, so dust-laden and so impossible to get at, that its outward form is no longer to be perceived.