We started at day-break, with a servant on the box, and two others preceding us on horseback, armed to the teeth. We changed horses every two or three hours, and the chamberlain having brought plenty of wine we refreshed ourselves now and again. The tour lasted a fortnight, and we stopped at five iron and copper manufactories. I found it was not necessary to have much technical knowledge to make notes on what I saw; all I required was a little sound argument, especially in the matter of economy, which was the duke's main object. In one place I advised reforms, and in another I counselled the employment of more hands as likely to benefit the revenue. In one mine where thirty convicts were employed I ordered the construction of a short canal, by which three wheels could be turned and twenty men saved. Under my direction Lambert drew the plans, and made the measurements with perfect accuracy. By means of other canals I proposed to drain whole valleys, with a view to obtain the sulphur with which the soil was permeated. I returned to Mitau quite delighted at having made myself useful, and at having discovered in myself a talent which I had never suspected. I spent the following day in making a fair copy of my report and in having the plans done on a larger scale. The day after I took the whole to the duke, who seemed well pleased; and as I was taking leave of him at the same time he said he would have me drive to Riga in one of his carriages, and he gave me a letter for his son, Prince Charles, who was in garrison there. The worthy old man told me to say plainly whether I should prefer a jewel or a sum of money of equivalent value. "From a philosopher like your highness," I replied, "I am not afraid to take money, for it may be more useful to me than jewels." Without more ado he gave me a draft for four hundred albertsthalers, which I got cashed immediately, the albertsthaler being worth half a ducat. I bade farewell to the duchess, and dined a second time with M. de Kaiserling. The next day the young chamberlain came to bring me the duke's letter, to wish me a pleasant journey, and to tell me that the Court carriage was at my door. I set out well pleased with the assistance the stuttering Lambert had given me, and by noon I was at Riga. The first thing I did was to deliver my letter of introduction to Prince Charles.