Hardly twenty-two months had passed since a previous earthquake had nearly destroyed the city of Cumanà. The people regard the reddish mist veiling the sky and the absence of a sea breeze at night as infallible ill omens. Many people came to see us to ask if our instruments predicted any further quakes. Their anxiety increased greatly when on the 5th of November, at the same time as the day before, there was a violent gust of wind, accompanied by thunder and a few raindrops. But no shock was felt.

Until the middle of the last century the mountains surrounding the Aragua valley were covered in forests. Huge trees of the mimosa, ceiba and fig families shaded the lake shore and kept it cool. The sparsely populated plain was invaded by shrubs, fallen tree trunks and parasitical plants, and was covered in thick grass so that heat was not lost as easily as from cultivated ground, which is not sheltered from the sun's rays. When the trees are felled, and sugar cane, indigo and cotton are planted, springs and natural supplies to the lake dry up. It is hard to form a fair idea of the enormous amount of evaporation taking place in the torrid zone, especially in a valley surrounded by steep mountains where maritime breezes blow, and whose ground is completely flat as if leveled by water. The heat prevailing on the lake shore is comparable to that in Naples and Sicily.

After dividing all that belongs to astronomy, botany, zoology, the political description of New Spain, and the history of the ancient civilizations of certain New World nations into separate works, many general results and local descriptions remained left over, which I could still collect into separate treatises. I had prepared several during my journey; on races in South America; on the Orinoco missions; on what hinders civilization in the torrid zone, from the climate to the vegetation; the landscape of the Andes compared to the Swiss Alps; analogies between the rocks of the two continents; the air in the equinoctial regions, etc. I had left Europe with the firm decision not to write what is usually called the historical narrative of a journey, but just to publish the results of my researches. I had arranged the facts not as they presented themselves individually but in their relationships to each other. Surrounded by such powerful nature, and all the things seen every day, the traveler feels no inclination to record in a journal all the ordinary details of life that happen to him.

The passage from the mouth of the Río Negro to Grand Para took only twenty to twenty-five days, so we could have gone down the Amazon as far as the Brazilian coast just as easily as returning by the Casiquiare to Caracas. We were told at San Carlos that political circumstances made it difficult to cross from Spanish to Portuguese colonies, but we did not know until our return to Europe what danger we would have been exposed to had we gone as far as Barcellos. It was known in Brazil, probably through newspapers, whose indiscretion is not helpful for travelers, that I was going to visit the Río Negro missions and examine the natural canal uniting the two river systems. In these deserted jungles the only instruments ever seen had been carried by the boundary commissioners. The Portuguese Government agents could not conceive how a sensible man could exhaust himself 'measuring lands that did not belong to him'. Orders had been issued to arrest me, seize my instruments, and especially my astronomical observations, so dangerous to the safety of the State. We were to be led along the Amazon to Grand Para, and then back to Lisbon. Fortunately, the Lisbon Government instantly ordered that I should not be disturbed but rather encouraged.