PRINCE IVAN LERMONTOFF came to consider the explosion one of the luckiest things that had ever occurred in his workshop. Its happening so soon after he reached St. Petersburg he looked upon as particularly fortunate, because this gave him time to follow the new trend of thought along which his mind had been deflected by such knowledge as the unexpected outcome of his experiment had disclosed to him. The material he had used as a catalytic agent was a new substance which he had read of in a scientific review, and he had purchased a small quantity of it in London. If such a minute portion produced results so tremendous, he began to see that a man with an apparently innocent material in his waistcoat pocket might probably be able to destroy a naval harbor, so long as water and stone were in conjunction. There was also a possibility that a small quantity of ozak, as the stuff was called, mixed with pure water, would form a reducing agent for limestone, and perhaps for other minerals, which would work much quicker than if the liquid was merely impregnated with carbonic acid gas. He endeavored to purchase some ozak from Mr. Kruger, the chemist on the English quay, but that good man had never heard of it, and a day’s search persuaded him that it could not be got in St. Petersburg, so the Prince induced Kruger to order half a pound of it from London or Paris, in which latter city it had been discovered. For the arrival of this order the Prince waited with such patience as he could call to his command, and visited poor Mr. Kruger every day in the hope of receiving it. One afternoon he was delighted to hear that the box had come, although it had not yet been unpacked. “I will send it to your house this evening,” said the chemist. “There are a number of drugs in the box for your old friend Professor Potkin of the University, and he is even more impatient for his consignment than you are for yours. Ah, here he is,” and as he spoke the venerable Potkin himself entered the shop. He shook hands warmly with Lermontoff, who had always been a favorite pupil of his, and learned with interest that he had lately been to England and America. “Cannot you dine with me this evening at half-past five?” asked the old man. “There are three or four friends coming, to whom I shall be glad to introduce you.” “Truth to tell, Professor,” demurred the Prince, “I have a friend staying with me, and I don’t just like to leave him alone.” “Bring him with you, bring him with you,” said the Professor, “but in any case be sure you come yourself. I shall be expecting you. Make your excuses to your friend if he does not wish to endure what he might think dry discussion, because we shall talk nothing but chemistry and politics.” The Prince promised to be there whether his friend came or no. The chemist here interrupted them, and told the Professor he might expect his materials within two hours.