"That's it," answered the shape.
"Now, I have a couple of hours to spare, and, if it would interest you, and you care to come over to my laboratory, I will be happy to give you one or two points which may prove of value to you—I say to my laboratory, but it really is not mine; I use any laboratory that is handiest, and I know most of the good ones in the city. You see, I do not need to have a key to enter a room; that is one of the great advantages we have, as you will discover one of these days. Just now I can get you in very well because the owner of the laboratory to which we will go is out of town. I will go in first and unlock the door for you."
I told him that I should be most happy to accept his invitation; it seemed the most natural thing in the world to be conversing with a ghost and to have him invite me to go to somebody's laboratory and use up his chemicals. It never occurred to me that it might not be considered quite good
form. We went out of my rooms and downstairs, the shadow floating alongside of me in the most friendly manner possible. I could see by the position of his body that he had hold of my arm, but his fingers did not show on my coat-sleeve.
We went up town for perhaps half a mile, and entered a large brick building in which I noted were various studios. It was dark, but going up three flights of stairs my guide opened a door and ushered me into a large and extensively furnished laboratory, evidently belonging to some scientific man of means and experience. The ghost turned the button of the electric light, and then motioned me to a seat.
"My time," he said, "is somewhat limited, because I have an appointment with a lady at twelve, but I will show you what a high explosive really is, and then if we have time we will talk of something else. The difficulty about high explosives is not in
making them, but in using them after they are made; you create a gigantic power which you do not know how to handle.
"The rather modern discovery of how to make liquid air has simplified matters a good deal. When you can make liquid hydrogen in quantities you will have a still better agent for many purposes. Now, let us take a little of this liquid air. You see it pours like water. As I happen to know, our absent host has nearly two gallons of it, or had this afternoon; some of it has evaporated, but, as you see, there is still more than a gallon left, and we will not steal much, as all we want for our experiment to illustrate to you the greatest explosive which can be manufactured is about as much liquid air as you can hold in a thimble."
"Do you propose to try your explosive here, Mr."—I hesitated. "By the way, what is your name?"