Neither of us had woken when the messenger came from Stahl to say that his preparations were complete and if we wished to attend on him at our earliest convenience we could witness his experiment. I cannot say that I felt up to a meeting with the irascible German in my drugged and shaky state, but Lower reluctantly concluded that it was our duty to do our best.
“God knows I don’t feel like it,” he said as he washed his mouth out and straightened his clothes before attacking a piece of bread and a glass of wine for his breakfast. “But if this has become a magistrate’s matter, then we will need to present our findings properly. Not that he is likely to pay us much attention.”
“Why not?” I asked with some curiosity. “In Venice physicians are regularly called to give their opinion.”
“In England as well. ‘Your honor, in my opinion this man is dead. The presence of a knife in his back indicates an unnatural death.’ As long as it is kept simple, there is no problem. Shall we go?” He stuffed more bread in his coat pocket and held open the door. “I’m sure you do not really want to miss it.”
Much to my surprise, Stahl seemed almost happy to see us when we dragged ourselves up his stairs and walked into his cramped and smelly lodging off Turl Street a quarter of an hour later. The prospect of demonstrating his ingenuity and skill to an appreciative audience was too much to resist, although he did his best to be churlish. Everything was ready—candles, bowls, bottles of various liquids, six little piles of powder—the stuff which he had extracted from the bottle—and chemicals Lower had purchased and sent round to him.
“Now, I hope you’re going to behave yourself, and not waste my time prattling.” He glared at us while Lower assured him that we would observe as quietly as possible—a statement which neither he nor Stahl believed for a moment.
The preliminaries done, Stahl settled down to work. As an example of chemical technique, it was fascinating to watch; and while he talked, I found my distaste slipping away in admiration at his ingenuity and methodical approach. The problem, he said, waving at the piles of powder, was perfectly simple. How do we determine what this sediment drawn from the brandy bottle is? We can look at it, but that demonstrates nothing, as many substances are white and can be reduced to powder. We can weigh it, but considering the amount of impurities present, that would prove little. We can taste it, and compare the taste to other things, but that operation—quite apart from the fact that it might be dangerous—would help little unless it had a unique and recognizable taste. From mere visual evidence we cannot say more than that the sediment is a whitish powder.
So, he said, warming to his theme, we must test it a little further—if, for example, we dissolved it in a little sal am-moniack, the mixture might respond in several ways—it might change color, or it might give off heat, or it might effervesce. The powder might dissolve, or float, or sink, still solid, to the bottom of the liquid. If we repeated the experiment with another substance, and it reacted in a similar fashion, could we then say that the two were the same?
I was about to reply in the affirmative, when he waved his finger at us. No, he said. Of course not. If they reacted differently, then indeed we might conclude that the two substances were not identical. But if they reacted in the same fashion, all we could say was that they were two substances which, when mixed with sal ammoniack, responded in the same way.
He paused while we digested this, then resumed once more. Now, you are thinking, he said, how can we possibly ascertain what this material is? And the answer is simple—we cannot. I told you this last week. Whatever you may think there can be no certainty. We can only say that accumulated evidence indicates the strong likelihood that it is such and such a substance.
I had not yet had much experience of law courts in England, but I knew that, if someone like Stahl went into a Venetian trial and spoke like that, the side he was supporting might as well abandon all hope.
“So, how do we do this?” he was asking rhetorically, waving his finger in the air. “We repeat the experimentation again and again and if, after every repeated experiment, the two substances match in their reaction, then we can conclude that the chances of their not being the same shrink to the point where to maintain they are different is unreasonable. Are you with me?”
I nodded. Lower didn’t bother.
“Good,” he said. “Now, I have in the last few days performed my experiments on a dozen or more substances, and have reached my conclusions. I am prepared here only to demonstrate them—1 have not the time to go through the whole process with you. I have here glasses containing five different substances, and we will add our powder one by one to all five, then begin the process of comparison. Now, the first is a little spirit of sal ammoniack,”—he poured a small amount of powder in as he spoke—“the second contains lixivium of tartar, then spirit of vitriol, spirit of salt and lastly, syrup of violets. I also have here a piece of hot iron. I hope you see the logic of this, Dr. Lower?”
Lower nodded.
“Perhaps, then, you would explain to our friend, here?”
Lower sighed. “This isn’t a lesson, you know.”
“I like people to understand the experimental method. Too many doctors do not; they merely prescribe potions without the slightest reason to think they might work.”
Lower groaned, then gave way. “What he is doing,” he said, “is subjecting the powders to all variants of matter. As you know, the essential principles of natural things are salt and earth, which are passive, and water, spirit and oil, which are active. The combination of ingredients he has chosen consequently covers all of these, and should provide an overall picture of every variety of matter. He is also testing heat, which is quite illogical of him, as he does not believe that fire is a natural element.”
Stahl grinned. “No, I do not. The idea that all matter contains a quantity of fire which can be released on heating I find unlikely. However, this is quite enough chatter. If your friend has got that into his pretty little head, we might begin.”
He peered at us closely to see he had our attention, then rubbed his hands together and picked up the first bowl, holding it to the light so we could see clearly.
“The sal ammoniack first of all. You see it has produced particles of a pale sediment with no other apparent movement. Hmm?”
He handed it over for our inspection and we agreed that the other substance he was showing us produced the same result.
“Now, lixivium of tartar. A white cloud in the middle of the liquid, suspended equidistantly between the surface and the bottom.”
Again, the other substance behaved in the same fashion.
“Vitriol. A precipitation producing hard crystals forming on the side of the glass. A matching result again.”
“Salt.” He paused and examined the bowl carefully. “A slight creamy precipitation, but so slight you might miss it entirely.
“Violets. How pretty. A tincture of pale green. Most attractive. Two of them, in fact, as my chosen substance has produced the same result. I hope you are beginning to be convinced.”
He grunted at us in a satisfied fashion, then picked up a pinch of each powder and threw them separately onto the red-hot iron. We watched as they hissed, and gave off thick white fumes. Stahl sniffed at them, then grunted again. “No flame in either case. Slight smell of—what would you say?—garlic.”
He poured some water on the iron to cool it down, then casually tossed it out of the window, so it could lie on the ground and not poison us. “And there we are. We needn’t waste any more time. We have now run a total of six separate tests, and in each case the material you brought me in the brandy bottle reacts in the same way as this substance here. As an experimentalist of chemistry, gentlemen, I offer you my opinion that the material in the bottle is indeed unlikely not to be the same.”