THE GALAPAGOS ISLANDS. 



27 



ancient stream of lava which has flowed down the 

 side of a peaked mountain, between two and three 

 miles distant from the station, in a direction nearly 

 north, and about two thousand feet high. The 

 peak slopes rapidly at first, forming a tolerably 

 steep cone, but terminated by a broad and gently 

 inclined base of a mile and a half. The mountain 

 is studded on every side with craters, or mouths, 

 from whence, at different periods, streams of lava 

 have issued, and running far into the sea, have 

 formed projecting points, such as that on which 

 we fixed our station. The western face of the 

 island presents a cliff nearly perpendicular, and 

 not less than a thousand feet high ; it exhibits the 

 rude stratification of lava, tuffa, and ashes, which 

 characterises the fracture of ancient volcanic 

 mountains. 



Abingdon Island is ten or twelve miles in length, 

 the north end being a series of long, low, and very 

 rugged streams of lava ; the peak standing about 

 one-third of the whole length from the southern 

 extreme. The rock at different places not far 

 from the station was found to be full of caverns, 

 into which the tide flowed and ebbed through sub- 

 terranean channels, the outer crust of the stream 

 having, as frequently happens, served as the pipe 

 to conduct the lava off. It is therefore probable 

 that our foundation may not have been the solid 

 rock ; a circumstance, which taken along with the 

 general hollow nature of volcanic districts, and 

 the deepness of the surrounding ocean, renders 

 these experiments not so fit to be compared with 

 those made in England, as with others made on a 

 similar volcanic sod. 



It was greatly to be regretted that our time was 

 too limited to allow of our engaging in a fresh 

 series, either at the same island, or on some other 

 lying near the equator ; the service upon which 

 the Conway was employed rendering it necessary 

 that our stay should not be longer at the Gala- 

 pagos than the 16th of January. But as we 

 anchored at Abingdon's Island on the 7th at noon 

 there remained barely nine complete days in which 

 everything was to be done. We had to search for 

 a landing-place, which occupied some considerable 

 time ; to decide upon a station ; to rig our tents ; 

 to build the observatory ; then to land the instru- 

 ments and set them up ; and, as we had no time 

 for trials and alterations, everything required to 

 be permanently fixed at once. We were fortunate 

 in weather during the first two days, when our 

 things were all lying about, and our habitations ill 

 assorted ; but on the third night it rained hard, 

 and the water, which trickled through the canvas, 

 caused us some discomfort, although we fortu- 

 nately succeeded in sheltering the instruments. 

 The heat, during the day, was not only oppressive 

 at the time, but very exhausting in its effects ; 

 and at night, although the thermometer never fell 

 lower than 73°, the feeling of cold, owing to the 

 transition from !)3°, to which it sometimes rose in 

 the day, was very disagreeable. 



It was with reluctance that I left the neighbour- 

 hood of the equator, without having made more 

 numerous and varied, and consequently less ex- 

 ceptionable, observations on the length of the 

 pendulum. It would above all have been desirable 

 to have swung it at stations whose geological cha- 

 racter more nearly resembled that of England 

 where Captain Rater's experiments were performed^ 



Thus the results obtained at the Galapagos, though 

 very curious in themselves, are not so valuable for 

 comparison with those made in this country. The 

 time may come, however, when they may be more 

 useful ; that is to say, should experiments be 

 made with the pendulum at stations remote from 

 the Galapagos, but resembling them in insular 

 situation, in size, and in geological character ; such 

 as the Azores, the Canaries, St. Helena, the Isle 

 of France, and various other stations amongst the 

 eastern islands of the Indian and the Pacific 

 Oceans. The advantage of having it swung at the 

 Cape of Good Hope, and especially at the Falkland 

 Islands, (which lie in the correspondent latitude 

 to that of London,) and at various other stations 

 on the main-land, or on large islands, is still more 

 obvious. 



The length of the seconds pendulum at the 

 Galapagos, as determined by our experiments, is 

 39.01717 inches, and the ellipticity or compression 

 of the earth, is expressed by the fraction ^-i^- ; 

 where the numerator expresses the difference 

 between the equatorial and polar diameters of 

 the earth, and the denominator the length of the 

 diameter at the equator. 



The details of these experiments have been 

 already published in the Philosophical Transactions 

 for 1823 ; and a general abstract is given in the 

 Appendix to this Part, No. III. 



We had no time to survey these islands, a 

 service much required, since ,few if any of them 

 are yet properly laid down on our charts. They 

 are in general barren ; but some of the highest 

 have a stunted brushwood, and all of them are 

 covered with the prickly pear-tree, upon which a 

 large species of land-tortoise lives and thrives in 

 a wonderful manner. These animals grow to a 

 great size, weighing sometimes several hundred 

 pounds ; they are excellent eating, and we laid in 

 a stock, which lasted the ship's company for many 

 weeks. 



The most accurate and full account of these 

 curious animals which I have anywhere seen, is 

 contained in a very amusing book, Delano's 

 Voyages and Travels, printed at Boston, in 1807. 

 From the fidelity with which such of their habits 

 as we had an opportunity of observing are de- 

 scribed, I am satisfied with the correctness of the 

 whole picture. We took some on board, which 

 lived for many months, but none of them survived 

 the cold weather off Cape Horn. I preserved one 

 in a cask of spirits, and it may now be seen in the 

 Museum of the College at Edinburgh : it is about 

 the medium size. Captain Delano says, — " The 

 Terrapin, or as it is sometimes called, the Land- 

 Tortoise, that is found at the Galapagos islands, 

 is by far the largest, best, and most numerous, of 

 any place I ever visited. Some of the largest 

 weigh three or four hundred pounds ; but their 

 common size is between fifty and one hundred 

 pounds. Their shape is somewhat similar to that 

 of our small land-tortoise which is found upon 

 the upland, and is, like it, high and round on the 

 back. They have a very long neck, which, 

 together with their head has a disagreeable ap- 

 pearance, very much resembling a large serpent. 

 I have seen them with necks between two and 

 three feet long, and when they saw anything 

 that was new to them, or met each other, they 

 would raise their heads as high as they could, their 



