O. sandwicensis, Gray, of Hawaii.
O. elliptica, Lab., of New Caledonia.

(e) O. parviflora, Schumann, of New Guinea, probably identical with O. mariannensis.

NOTE 58 (page 156)
 
On Pandanus (from Warburg)

(a) The size (length) of the drupes of endemic species in oceanic islands.—The drupes of P. reineckei of Samoa are 4-5 cm. (1³⁄₅-2 inches). Those of P. joskei and P. thurstonii in Fiji measure respectively 6 cm. (2²⁄₅ inch) and 2¹⁄₂ cm. (1 inch).

Out of about sixteen species in the Mascarene Islands (Mauritius, Réunion, and Rodriquez) quite half have drupes 2-3¹⁄₂ cm. (⁴⁄₅-1²⁄₅ inch) in size, whilst they run up to 8 or 10 cm. (3-4 inches), and may be less than a centimetre (²⁄₅ inch).

(b) The affinities of the Fijian and Samoan species.

NOTE 59 (page 188)
 
Seeds in Petrels

Darwin, in his correspondence (1859) with Sir Joseph Hooker, refers to the occurrence of large West Indian seeds in the crops of some nestling petrels observed by Sir William Milner at St. Kilda (Life and Letters, II, 147, 148). Mr. Charles Dixon in Ibis (1885) refers to Sir W. Milner’s observation in the case of the Fulmar Petrel (Procellaria glacialis) and speaks of them as Brazilian seeds brought by the Gulf Stream, adding that he himself found a nut in the crop of one of these birds in the same locality. He supposes that the birds pick them up from the water. Mr. Hemsley very kindly wrote to Sir Joseph Hooker recently on this point with the object of obtaining some idea of the nature of the seeds; but after this lapse of time it has not been found possible to satisfy my curiosity. I live in the hope of their proving to be Cæsalpinia seeds.

NOTE 60 (page 202)
 
Schimper on the Halophilous Character of Littoral Leguminosæ and of Shore Plants generally

As a result of extensive microchemical investigations, this eminent German botanist arrived at the conclusion that plants living on the sea-shore, or in inland stations rich in chlorides, are able, as a rule, to store up in their tissues a large quantity of these salts, a capacity enabling them to live in localities where the subsoil is rich in these materials. This inference, as shown in his experiments, is just as applicable to the shore-plants of temperate regions, such as Aster tripolium, Crambe maritima, and Eryngium maritimum, as it is to such typical littoral plants of the tropics as Barringtonia speciosa, Ipomœa pes capræ, Scævola Koenigii, Tournefortia argentea, &c. However, with the Leguminosæ experimented upon, this capacity of storing up chlorides was often exhibited but slightly or not at all; and characteristic Pacific beach-plants, such as Canavalia turgida, Pongamia glabra, and Sophora tomentosa are especially cited as examples (Schimper’s Ind. Mal. Strand-flora, pp. 140-151; Wolff’s ash-analyses are here quoted).

The summit is formed of bare rock and sand, the phanerogamic vegetation ceasing a couple of thousand feet below. Some low plant-forms doubtless occur under the moist, warm conditions near the steam-cracks, since Wilkes mentions his finding a small moss; but with this exception the surface may be described as sterile.

Dryness of the Air and Electrical Phenomena.—Wilkes refers to the association of these conditions more than once in his narrative. Whenever, as sometimes happened, the dew point could not be obtained with Pouillet’s hygrometer, electricity was easily excited, and was developed in large sparks. On taking off the clothes at night, sparks would appear. As shown in the table subjoined, electrical phenomena were noticed during the first few days of my sojourn on the summit when the relative humidity was very low. My red blanket at night crackled in my hands and emitted sparks, and a glowing line was produced by drawing the finger along. Whilst the air was in this condition I observed that the wings of dead butterflies lying on the ground stuck to my fingers tenaciously like a needle to a magnet. The adhesiveness disappeared when the excessive dryness gave place to humidity. The physiological effect on me of the associated dryness and electrical state of the air was displayed in a hot, dry, sweatless skin (cracking and chapping rapidly), severe headache and sore-throat, general lassitude, and great irritability. When the weather changed and the air became humid, these unpleasant symptoms quickly disappeared.

As a result of these dry conditions on the summit of Mauna Loa, decomposition does not occur. I found in one place on the top, on the site of an old camp, the remains of a quarter of beef, the meat fresh but dried up. From a water-bottle left behind by one of the party and subsequently restored to him, I learned that the visit had been made in the previous summer. This non-decomposition seems a little strange, since, as remarked below, flies and other insects were not infrequent on the summit. However, as Hann remarks, when speaking of mountain climates, everything dries much more quickly at great altitudes; animals that have been shot, or killed by falling, become mummies without undergoing decay (Schimper’s Plant-Geography, 697).... The scorching power of the sun in a sky usually cloudless, or nearly so, was a trying feature of my daily experiences; and I found that when I faced it with unshaded eyes during my walks I suffered from severe pain in the eyeballs at night.

Insects on the Summit.—It may seem a strange thing to relate, that in a region apparently absolutely sterile, the flies and other winged insects caused me much discomfort in my small tent when I was confined to it through illness. When lying down one morning I noticed the house-fly, the blue-bottle, and two or three other flies, small beetles not over a fifth of an inch in size, a moth, and a wasp. They were no doubt quite happy in the heat, as the temperature inside was over 80° F., and the sun’s rays felt almost scorching through the thin duck canvas. Butterflies (and occasionally large moths) were often observed flying in a drowsy condition about the summit and were easily caught. They were fond of fluttering around the steam-holes. In places, numbers were to be seen dead and dried up on the ground, the detached wings lying about. In the case of a recently dead butterfly I found its carcase already attacked by numerous small bugs. The butterflies were most frequent when there was a fresh southerly breeze, and were doubtless blown up the slopes from the forests below.

Whymper in his Travels amongst the Great Andes of the Equator gives many particulars of the occurrence of insects at great elevations. He noticed beetles, diptera, butterflies, moths, and several other insects at altitudes of 15,000 to 16,000 feet. At 16,500 feet he obtained a small bug of the genus Emesa. He quotes Humboldt and Bonpland as showing that insects are transported into the upper regions of the atmosphere 16,000 to 19,000 feet above the sea, and he remarks that the transportation of insects by ascending currents of air has occasionally been observed in operation. These facts bear directly on the dispersal of insects.

The Winds.—My tent, which was pitched near the middle of the western border of the crater, happened to be situated in the battle-ground of the northerly and southerly winds, in a region of gusty winds, fitful airs, and dead calms. The northerly winds were usually from N.-N.N.W. and the southerly winds from S.W.-S.S.W., easting in either case being rarely observed, the northerly winds rather prevailing at night. As a result of this location miniature whirlwinds were frequent in the vicinity of my tent, which carried sand into the air and more than once threatened to lift up my tent bodily and carry it off into the crater below. At the north end of the crater-border north-easterly winds prevailed, and at the south end southerly winds occasionally showing easting. When on one occasion I walked round the crater-margin, a fresh south-easterly wind prevailed at most parts of the circumference except in the vicinity of my camp, where there was a light S.S.W. wind both at 8 a.m. and 6 p.m. when I started and returned. The local character of the winds was often displayed in my walks. On one occasion, having left my camp, where a southerly wind was blowing, and walked half a mile to the north, I found a bitterly cold N.N.E. gale in my face which so impeded my progress that I returned to my camp where the same southerly breeze continued.

Commodore Wilkes was encamped on the east side of the crater, and there (December and January) he experienced strong south-west winds, on at least three days having the force of a gale. These are the prevailing winds in this season over the group; whereas in August, the time of my sojourn, south-westerly winds are quite out of season, this being in the midst of the period of the N.E. trades.

It will be gathered from the foregoing remarks that the mere record of the winds is insufficient for the purpose of obtaining any definite notion of the air-currents at this elevation (13,600 feet). It is to close observation of the clouds that we must look for data of importance.

The Clouds.—The clouds on the summit of Mauna Loa were an unending source of interest to me, and I will give briefly the results of my observations. The highest clouds were wispy cirri, often arranged as in a mackerel sky, and evidently at a great altitude. They were only observed on four or five days. (The lower clouds are indicated in the accompanying diagram.) Below them and at no great height above the mountain were to be not infrequently observed isolated woolly clouds that were carried in a few minutes across the sky and had a brief existence, often forming and melting away as one gazed at them. Next, there was a heavy bank of cumulus, which formed on the south-west slope near the top of the mountain, from which lines of cloud extended along each flank. Lowest of all was a broad belt, or rather a sea, of cumulus that was developed on both sides of the mountain about one-third way down its slopes, and during the day-time isolated the peak from the world below. It is with the last two cloud formations that we are most concerned, and I will first describe the sea of cumulus.

The sea of cumulus, as in the case of similar cloud-formations of most other isolated mountains, when viewed from above, as from the mountain-top, presents a cloud-field of dazzling whiteness, sparkling in the sun. Seen from below, as from the coast, it has the dark lowering appearance of the rain-cloud and indicates the rain-belt. Disappearing during the night, this broad belt begins to form again between 8 and 9 a.m., and by 10 or 11 a.m. the lower regions are completely hidden and the mountain’s summit, cut off from the world, rises above the level of the sea of clouds like an island in an Arctic ocean. As the day progresses the clouds become more compact and dense. The usual altitude of this broad belt of cloud is between 7,000 and 8,000 feet. This level is indicated by the burying of the Kohala mountains, which rise to a height of 5,500 feet in the distant north-west corner of the island, and by the usual emergence of the highest summit of Hualalai, which rises, still nearer, to an elevation of 8,275 feet. On some days, however, it attains a height of nearly 9,000 feet. On such occasions the highest peak of Hualalai kept reappearing and disappearing during the day, but the distant summit of Haleakala in East Maui, 10,032 feet in elevation and 80 miles away, was always visible.

Words fail to describe the magnificent aspect of this sea of cloud which shuts off the spectator from the world below. From the summit of the mountain he gazes down on its surface lit up by a sun shining in a typically cloudless sky. At one time it appears as an undulating Arctic land covered with snow of dazzling whiteness. At another time it looks like a hummocky frozen Polar sea sparkling in the sunshine. Through occasional rifts, however, one can discern a dark dismal region of mist and rain-cloud beneath. Miss Bird, who passed a night on the summit in June, 1874, well describes this sea of cloud in her book on the Sandwich Islands as “all radiance above and drizzling fog below.”

The heavy bank of cumulus, that forms at noon on the south-west slope at an altitude of 10,000 to 13,000 feet above the sea, and sometimes rises above the mountain, is one of the most conspicuous of the cloud-phenomena on the summit of Mauna Loa. Apparently extending from it, but in reality moving towards it, are two lines of small cumuli that follow the same level along either flank above the sea of cumulus, as is indicated in the accompanying diagram. It was observed by Wilkes in mid-winter, 1840-41, but at a lower level. “Clouds would approach us (he writes) from the south-west when we had a strong north-east trade wind blowing, coming up with their cumulus front reaching the height of about 8,000 feet, spreading horizontally and then disappearing.” During my sojourn this bank formed a very striking feature in the landscape during the early afternoon. On two or three occasions when I visited the south side of the summit and descended for about a thousand feet I passed through this bank, being then exposed to a driving mist coming up the slopes from the south-west. Though its upper surface viewed from a distance is dazzling white, below it is dark and nimboid.

It is to an updraught of warm moist air on the south or south-west slopes of the mountain, and to the prevailing cool north-east trade that strikes the north side of the summit, that we must look for the explanation of the development and situation of this bank. Although the trade-wind is markedly stronger than the south-west updraught, some of the warm, moist, southerly air-currents find their way, as shown by the observations at my camp, along the sides of the summit, and a line of condensation is produced where they come into contact with the cool air of the north-east trade as it sweeps past the flanks of the mountain. Sometimes at my camp, when there was a light southerly breeze blowing, I have noticed the line of small cumuli moving south along the mountain side towards the bank of cumulus.... I may remark that on a few days a small bank of cumulus formed under similar conditions on the north-west side of the summit.

From my study of the clouds I arrived at the conclusion that there were three prevailing air-currents on the summit of Mauna Loa:

(1) The updraught of warm moist air on the south and south-west slopes of the mountain.

(2) The north-east trade wind, the upper limit of this air-current being probably not far above the summit.

(3) An upper air-current from the south-east (E.S.E.-S.S.E.), which, from the velocity of the clouds it carried, was often probably not over a couple of thousand feet above the summit. It may be observed that on the coast at the base of the southern slope of the mountain in the middle of September, when the wind was N.E. and carried the lower clouds with it, the upper clouds were, on several occasions, noticed travelling in the opposite direction, namely, from the south.

The volcano was quiescent during my visit and could have exercised but little influence on the air-currents.

The Shadow of the Mountain.—Every morning and evening, in clear weather, for about twenty minutes after sunrise and before sunset, the shadow of the mountain was thrown back against the sky of the opposite horizon. It seemed as if some Titanic brush, at work in the sky far away, had painted in the profile of the mountain with a very uncanny blue. At sunset the peak was the last to disappear. Commodore Wilkes, who only records it once, namely, at sunset on the 1st of January, describes it as “a beautiful appearance of the shadow of the mountain projected on the eastern sky ... as distinct as possible, its vast dome seemed to rest on the distant horizon.” This phenomenon is, of course, well known in the case of other isolated mountains. According to Murray’s Handbook of Southern Italy (1892), the correct thing for a visitor to Stromboli is to make an early ascent of the cone to observe “the very curious triangular shadow of the mountain cast by the rising sun upon the sea.” Unfortunately I neglected my opportunity when on the island. The shadow of the mountain is also one of the sights of Etna, a dark-violet, triangular shadow (Baedeker) being thrown at sunrise over the surface of West Sicily, that is, on the land. I saw the shadow but imperfectly outlined, as the weather was not favourable at the time of my ascent. When at Nicolosi, on the south slope of Etna, I noticed at sunset a faint shadow of the mountain thrown against the eastern sky. I gathered from a short conversation with Prof. Ricco, the director of the Catania Observatory, when I told him of the shadow of the Hawaiian mountain, that the interest lay in its projection against the sky. It is doubtless akin to the spectre of the Brocken and other mountain spectres.

Some Previous Meteorological Observations on Mauna Loa.—.... Mr. Douglas, the botanist, who was subsequently found dead in a cattle-pit on Mauna Kea, spent a day on the summit of Mauna Loa in the middle of January, 1834. He mentions that a little way below the top the thermometer fell at night to 19° F. The wind on the top was N.W. The air at 11.20 a.m. was 33°, the hygrometer registering 0·5. He remarks that the great dryness of the air was evident without the assistance of the hygrometer (Hawaiian Spectator, vols. I and II, 1838-9).

Commodore Wilkes, in vol. IV of his Narrative of the United States Exploring Expedition, gives the following observations on the temperature and winds on the top of Mauna Loa between Dec. 23, 1840, and Jan. 13, 1841. Those on the temperature are incomplete, but they give a fair idea of the prevailing conditions. The degrees are in Fahrenheit’s scale.

• Dec. 23, 1840: elevation, 13,190 feet; 3 p.m., 25° F.; strong S.W. gale; night temperature, 15°.
• Dec. 24, 1840: summit (13,600 feet); night minimum, 22°.
• Dec. 26, 1840: summit (13,600 feet); violent S.W. gale; night min., 17°.
• Dec. 27, 1840: summit (13,600 feet); sunrise temp., 20°; night min., 17°; wind, S.W.
• Dec. 29, 1840: summit (13,600 feet); noon temp. in shade, 47°; night min., 20°.
• Dec. 30, 1840: summit (13,600 feet); noon temp., 55°; night min., 13°.
• Dec. 31, 1840: summit (13,600 feet); night min., 17°.
• Jan. 2, 1841: summit (13,600 feet); sunrise, 20°; wind, N.E.
• Jan. 3, 1841: summit (13,600 feet); night min., 17°.
• Jan. 4, 1841: summit (13,600 feet); daylight, 20°.
• Jan. 8, 1841: summit (13,600 feet); S.W. gale.
• Jan. 10, 1841: summit (13,600 feet); night temp., 16°.
• Jan. 12, 1841: summit (13,600 feet); night temp., 17°.
• Jan. 13, 1841: summit (13,600 feet); strong S.W. wind.

The usual variation of temperature in the twenty-four hours is given as 17°-50°. The south-west was evidently regarded as the prevailing wind, and the clouds are spoken of as sometimes moving from opposite directions towards the same centre.

When Miss Bird spent a night on the summit of Mauna Loa during the eruption of June, 1874, the cold was described as intense, eleven degrees of frost (21° F.).

Observations on the Summit of Mauna Kea.—.... When Prof. Alexander with a party of scientists ascended this mountain (in the summer of 1892), the thermometer at night fell to 13° F., and the trade-wind was found to be blowing as strongly on the summit as down below (Whitney’s Tourist Guide to Hawaii). It is to be inferred that the party camped by the small lake which is a few hundred feet below the actual summit (13,800 feet). This lake, which I visited on May 20, 1897, is about 120 yards across, and evidently shallow, probably not more than three or four fathoms deep. A carpet of algæ covered the bottom. At noon, by the lake, the air in the shade was 53° F., whilst the temperature of the surface-water was 51°. The lower clouds were moving from S.S.E. This lake is said to be permanently frozen over in the winter, and to have been visited by skaters.

Permanent Water Supply on the Summit of Mauna Loa.—In this barren rocky region water derived from the winter-snow is to be found all the year through at the bottom of the deep cracks or fissures in the lava-rock. Such fissures are from two to four feet wide, and in the case of that near my tent the bucket had to be lowered to a depth of seventeen or eighteen feet to reach the water, or rather the ice, since it was often necessary to break the surface ice. In these deep, narrow fissures, which the sun scarcely penetrates, the water would probably be frozen over all through the seasons; but in those of less depth it would remain liquid in summer.

Register of Observations on Wind, Relative Humidity, Cloud, Rain, and Temperature, made by H. B. Guppy on the Summit of Mauna Loa at an Elevation of 13,500 Feet above the Sea, August 9th to 31st, 1897. (Camp about Middle of West Side of Crater Margin)