Two main questions confront the student of Darwin’s historic visit: Where did Darwin go, and exactly how did his visit affect his scientific thinking? Answering the first turns out to be easier than one might think, thanks to a rich repository of documentary sources. The British Navy had a penchant for keeping detailed records, and the Beagle’s voyage is described in three ship’s logs, Captain FitzRoy’s personal narrative, a series of excellent maps made by the Beagle’s officers, and various watercolors and sketches by crew members. We are also able to draw on Darwin’s own extensive record of his dozen or so field trips, which encompasses more than 100 pages of unpublished notes and more than 80 pages of published material.
For five years the Beagle’s logs recorded, often on an hourly basis, where the ship was and what it was doing. Two days after the first sighting of land in the Galápagos, on September 15, 1835, the Beagle anchored in Stephens Bay on Chatham Island, now known as San Cristóbal. (All the islands were given Spanish as well as English names by their early visitors, who included Spaniards seeking Inca gold and silver in Peru, and British buccaneers intent on stealing these riches from the Spanish.) From this anchorage, the Beagle officers recorded a bearing of N10ºE to Kicker Rock, an impressive 470-foot islet about four miles off the shore, and a bearing of N45ºE to Finger Hill, a 516-foot tuff crater. When drawn on a map, the place at which these two bearings cross indicates the Beagle’s point of anchorage. Using other bearings in the Beagle’s logs, together with Darwin’s remarks in his diary and scientific notes, it is possible to reconstruct virtually all of Darwin’s landing sites and inland treks during his five-week visit. These include many regions that are either in remote or potentially dangerous locations and hence off limits to tourists.
As the Beagle sailed from east to west through the archipelago, Darwin visited four of the larger islands, where he landed at nine different sites. On San Cristóbal, Darwin was particularly drawn to a heavily “Craterized district” on the rugged, northeastern coast. “The entire surface of this part of the island,” Darwin reported, “seems to have been permeated, like a sieve, by the subterranean vapours: here and there the lava, whilst soft, has been blown into great bubbles; and on other parts, the tops of caverns similarly formed have fallen in, leaving circular pits with steep sides. From the regular form of the many craters, they gave to the country an artificial appearance, which vividly reminded me of those parts of Staffordshire, where the great iron-foundries are most numerous.”
As Darwin explored San Cristóbal, he encountered many birds and animals new to him. He marveled at the remarkable tameness of the birds, pushing a curious hawk off a branch with the barrel of his gun, and trying to catch small birds with his hands or in his cap. He also noted the striking dominance of reptiles within these islands, which made the archipelago seem like a journey back in time. On the shoreline were swarms of “hideous-looking” marine iguanas—the world’s only oceangoing lizards. On land, the Beagle crew encountered large land iguanas, closely allied to their marine cousin; a couple of smaller lizards; a snake; and giant land tortoises, after which the islands are named. (The old Spanish word galápago means saddle, which the shape of the tortoise’s carapace resembles.)
In the midst of a partly vegetated lava field on San Cristóbal, Darwin came upon two enormous tortoises, each weighing more than 200 pounds. One, he noted, “was eating a piece of cactus, and as I approached it, it stared at me and slowly stalked away; the other gave a deep hiss, and drew in its head. These huge reptiles, surrounded by the black lava, the leafless shrubs, and large cacti, seemed to my fancy like some antediluvian animals.” Altogether these giant reptiles contributed dramatically, Darwin thought, to the “strange Cyclopean scene.”
Floreana was the next of the four islands Darwin visited. The first settlement in the Galápagos had been established there just three years before, populated by convicts from Ecuador; it collapsed a few years later, after some malcontented prisoners took up arms against the local governor. On Floreana, Darwin remarked in his private diary, “I industriously collected all the animals, plants, insects, & reptiles from this Island”—adding, “It will be very interesting to find from future comparison to what district or ‘centre of creation’ the organized beings of this archipelago must be attached.” Still thinking like a creationist, Darwin was seeking to understand the islands’ strange inhabitants within the ruling biological paradigm.
After a brief stop at Tagus Cove, on Isabela, the Beagle headed for Santiago. Darwin, three crew members and his servant, Syms Covington, were left for nine days to collect specimens while the Beagle returned to San Cristóbal to obtain fresh water. Guided by a settler from Floreana who had been sent to hunt tortoises, Darwin ascended to the highlands twice to collect specimens in the humid zone. There he was able to study, in considerable detail, the habits of the tortoise.
These lumbering behemoths, he found, came from all over the island to drink water at several small springs near the summit. Hordes of the giants could be seen coming and going, with necks outstretched, burying their heads in the water, “quite regardless of any spectator,” to relieve their thirst. Darwin counted the number of times that the tortoises swallowed in a minute (about ten), determined their average speed (six yards a minute), and studied their diet and mating habits. While in the highlands Darwin and his companions dined exclusively on tortoise meat. He commented that it was very tasty when roasted in the shell or made into soup.
When he was not collecting specimens, Darwin devoted time to trying to understand the islands’ geological features, especially the prominent tuff cones near his campsite at Buccaneer Cove. He was the first geologist to appreciate that such sandstone-like structures, which rise to a height of more than 1,000 feet, owe their peculiar features to submarine eruptions of lava and mud; they mix at high temperatures with seawater, producing tiny particles that shoot into the air and rain down on the land to form huge cinder cones.