5«2 



NATURE 



[October 9, 1890 



THE VOLCANOES OF THE-,TABLE LAND 

 OF MEXICO. 



THE following account with extracts is based on information 

 gathered from a notice which appeared in the Phila- 

 delphia Public Ledger, sent us by the courtesy of Prof. 

 Heilprin. He had been obliged to issue the notice in advance 

 of the full publication of his papers by the Academy of Natural 

 Sciences of Philadelphia, as he found on his return many varying 

 reports of the work carried on in Mexico. 



Amongst the most recent determinations of the heights of 

 these great volcanoes are those made by the Mexican Expedition 

 lately organized under the auspices of the Academy of Natural 

 Sciences of Philadelphia. Prof. Heilprin has recently placed 

 on record his barortietric determinations of the four loftiest 

 summits of the Mexican Republic : Orizaba, Popocatepetl, 

 IxtaccihuatI, and the Nevado de Toluca. In this paper he 

 points out that the highest point of the Republic is the Citlal- 

 tepetl or Star Mountain, more commonly called the Peak 

 of Orizaba, and not Popocatepetl as is generally assumed by 

 the Mexican geographers. All his observations were made 

 " with a carefully tested aneroid barometer, and the data were 

 computed from almost simultaneous observations at the Mexican 

 Central Observatory of the City of Mexico, and from barometric 

 readings made at the sea-level at Vera Cruz. The equable 

 condition of the atmosphere, at the time these observations were 

 made, rendered the possibility of the occurrence of. possible 

 errors of magnitude almost nil." From the above quotation it 

 will be seen that great care was taken to eliminate all errors and 

 to get as accurate measurements as possible. 



Popocatepetl was commonly accepted as the highest peak, and 

 Alexander von Humboldt recorded it in 1804 as 17,720 feet. 

 Since the above date, many trigonometrical surveys have been 

 made, and the results vary from 17,200 feet to a few feet over 

 18,000. The latest measurements by Prof. Heilprin give 

 17,523 feet as the height, being 200 feet lower than Humboldt's 

 estimate. This determination has been derived from the newer 

 data which have been made possible through the levelling of 

 the Mexican Railway, which was constructed a few years since, 

 while geographers have almost universally accepted Humboldt's 

 determinations and figures. From these new data it was shown 

 that "the estimate of the elevation of the city of Mexico 

 (7470 feet), and of the adjoining plateaus, which have served as 

 a basis for most of the angle measurements of the mountains, 

 have been placed 123 feet high. Allowing for this excess, 

 a striking correspondence is established between the early 

 measurements and those obtained in the spring of the year 

 by the Philadelphia Expedition." 



Prof. Heilprin and Mr. F. C. Baker made the ascent of this 

 mountain on April 16 and 17, reaching the "rim of the crater 

 at 11.30 o'clock on the morning of the 17th, and the cul- 

 minating point early in the afternoon of the same day. Little 

 difficulty was encountered in the ascent beyond that which is 

 due to inconvenience arising from the highly rarefied atmosphere. 

 The snow-field was found to be of limited extent, and not more 

 than from five to ten feet in depth, and was virtually absent from 

 the apex of the mountain. The surprisingly mild temperature 

 of the summit, 45° Fahrenheit, rendered a stay of several hours 

 in cloud land very delightful." 



The supposed second highest summit of the Mexican Republic 

 is the mountain of Orizaba or Citlaltepetl, and "the results of 

 Prof. Heilprin's determinations show more marked variations 

 from those of most of the earlier investigators, and more 

 particularly from those of Humboldt." The height determined 

 by Humboldt by means of angles taken from near the town of 

 Galapa, was 17,375 feet, while Ferrer's determination in 1796 

 gave 17,879 feet, as recorded in the Transactions of the American 

 Philosophical Society. The latter value is generally adopted by 

 the German geographers, while the Mexican geographers, on ihe 

 other hand, adopted the measurement of Humboldt, or "that 

 which was obtained by the National Commissions of 1877, 

 indicating a height of 17,664 feet." 



The following is a short account of the ascent: — "Prof. 

 Heilprin, with three of his scientific associates and eleven 

 guides, made the ascent on April 6 and 7, or ten days before 

 the ascent of Popocatepetl. The last camp, at a height of some 

 13,000 feet, was left shortly before five o'clock in the morning 

 of the second day, and after a difficult and continuous struggle 

 of twelve hours through loose boulders, sand, and a much cut 

 up ice cap, the party — or rather the fragment which succeeded 



NO. 1093, "^O^- 42] 



in holding out — finally reached the rim of the crater." At this 

 point, about 120 feet below the apex of the cone, Prof. Heilprin 

 made a measurement which indicated a total height of 18,206 

 feet, exceeding Ferrers and Humboldt's measures by 325 and 

 800 feet respectively. 



As upon Popocatepetl, "the snow cap, upon Orizaba, al- 

 though arising 2400 feet, or nearly half a mile above the summit 

 of the highest peak of the Alps, was a comparatively insigni- 

 ficant development." The time spent on the summit was 

 short, lasting only a quarter of an hour, and then followed 

 the descent through the numerous seracs of the ice, which 

 proved most difficult. At a little past eight o'clock in the 

 evening the camp was reached, thus completing "a remarkable 

 round of mountain climbing of fifteen successive hours." 



Prof. Heilprin describes the views from the slopes of the 

 mountain as surpassingly grand, exceeding anything that he had 

 seen in his travels. " Far off to the west the giants Popocatepetl 

 and IxtaccihuatI were clearly outlined against the sky at a 

 distance of about 100 miles, while to the east and south the eye 

 wandered over a seemingly endless expanse of plateaus and low- 

 lands, penetrating through a series of successive cloud planes." 

 The measurements of both the peaks of Orizaba and Popo- 

 catepetl were made under very similar conditions of the atmo- 

 sphere ; the same instruments were used, and there was only an 

 interval of ten days between the measurements, which points to 

 the conclusion that "the first place among Mexican volcanoes 

 must be accorded to the Star Mountain." 



On the 27th of the same month the ascent of the third highest 

 peak, called the IxtaccihuatI, was made. The general appear- 

 ance of this mountain differs considerably from the two men- 

 tioned above ; instead of having a symmetrical or conical out- 

 line, it has " a strong flowing crest, covered with a heavy 

 deposit, some 75 or 100 feet in thickness, of snow and ice, 

 which serves readily to distinguish the familiar ' White 

 Woman ' of the plain of Anahuac." 



The measurement obtained by Prof. Heilprin of the height 

 of this mountain is 16,962 feet, which height differs by 800 to 

 1300 feet respectively, from those formerly obtained by the 

 Mexican geographers. Sonntag, in the year 1857, also deter- 

 mined its height, and his result accords very closely (within 

 II feet) with Prof. Heilprin's. The temperature on the summit 

 was found to be lower than that on either of the other two 

 peaks, the thermometer indicating 32° F. 



In view of the close proximity of this mountain to Popo- 

 catepetl, it is difficult "to account for the low value given by 

 Humboldt and the Mexican geographers. So nearly do they 

 appear of equal height that the eye at first fails to distinguish 

 which of the two summits is the higher. German geographers, 

 however, in a few cases, have adopted Sonntag's measurements, 

 neglecting, as in the case of Popocatepetl, to make allowances 

 for the error in this case of 125 feet which is indicated by the 

 levelling of the Mexican Railway." 



On April 2, Prof. Heilprin and Mr. Baker ascended the fourth 

 highest summit of the Republic, the Nevado de Toluca. The 

 ascent of this mountain is much easier than the others, and the 

 summit can be reached on horseback to within a distance of 900 

 feet. The rim of the broken crater " is extremely ragged and 

 narrow, descending with equal abruptness to the inner and outer 

 faces of the volcano. At some points the crest is so attenuated 

 that it can be readily straddled." The height of this mountain 

 was found to be 14,952 feet, which approximately corresponds 

 to the mean between Humboldt's determination and those made 

 by a class of students from the School of Engineers of the city 

 of Toluca. 



The results of the measurements of this mountain are very 

 divergent, as will be seen by the following list. La Perouse, in 

 1786, gave the height as less than 13,000 feet. The British 

 Hydrographic Chart of 1872 gave 14,970 feet, and this estimate 

 is the one which is generally followed by the English and a 

 number of American geographers. Malespina, in 1791, by 

 means of angles taken from positions near Fort Mulgrave, 

 determined the height to be 17,851 feet, while Tebenkoff re- 

 duces this figure by about 900 feet. 



The most carefully conducted series of measurements are 

 "those which were made by Mr. W. H. Dall, under the 

 auspices of the United States Coast Survey, 1874. These yielded 

 results ranging from a little more than 18,000 to nearly 20,000 

 feet. The measurements were made from distances 69, 127, and 

 167 miles, and it is more likely that the discrepancy in the results 

 obtained is due to an uncertainty regarding the actual position of 



