Notes on Mauna Loa in July, 1888. 51 



Art. V. — Notes on Mauna Loa in July, 1888. 



I. On an Ascent of Mount Loa by W. C. Merritt, President of 

 Oahu College. From a letter to J. D. Dana, dated July 28. 



President Merritt reached the summit of Mt. Loa at 

 noon of the 18th of last July, and encamped near the southeast 

 angle of the crater. The spot was considerably lower than the 

 highest point on the west side of the crater, and probably about 

 13,400 feet above tide-level. Water boiled at 185° F. between 

 7 h and 8 h in the morning when the temperature was at 56° F. 

 The thermometer was at 62° F. at noon, 40° F. at 7 P. M., 30° 

 F. at 11 P. M. and 26° F. at daybreak, so that during the night 

 water froze in a large crack, ten feet below the surface. About 

 half a mile south-by-west from the southern end of the crater 

 of Mokuaweoweo (see map, Plate II, vol. xxxvi), there was 

 a small but deep pit-crater. Having descended the east wall 

 of the central pit of Mokuaweoweo to its bottom, a small 

 cinder cone was found not far from the eastern wall ; and just 

 southwest, a pumice cone in the midst of an aa flow, the sum- 

 mit of which was very hot and reddish from the action of va- 

 pors. In the southwest corner of the pit, there was a cone at 

 F (for all positions see same map), from which vapors were 

 escaping, and south of it, at m, a circular pit 300 and 400 feet 

 in diameter by estimate, and 150 to 175 feet deep. The walls 

 of the pit consisted of the edges of layers of basaltic rock 

 one of which was 40 to 50 feet thick, and vertically columnar 

 in structure. The floor of the central pit had, as a whole, a 

 slope from the southwest to the northeast, confirming the view 

 that the southwest part of the pit had been the seat of great- 

 est activity, as it is in Kilauea. Southwest of m, the outer 

 wall of the central pit was cut through from top to bottom 

 by two parallel fissures, which had a S.S.W. direction, and 

 thence pointed nearly toward the place of chief eruption of 

 1887. East of m and near the wall in the direction of L, 

 there were great numbers of small fumaroles, from which 

 sulphur vapors were escaping freely, and large deposits of 

 sulphur had been made about them. Near h two dikes, 2 to 2^ 

 feet thick, intersected the walls, crossing one another at a 

 small angle, the rock of which had a feldspathic aspect. 



From a rough measurement, the depth of the crater on the 

 east side was made not over 350 feet. If this small depth is 

 sustained by careful observations, a great change of level had 

 taken place since the survey of Mr. Alexander in 1885. Such 

 a change might have been among the effects of the eruption 

 of February, 1887. 



