AND OF THE PHYSICAL SCIENCES. 



31 



MINERALOGY. 



The Matta>I DiaMOKD. — The Kajah of Mattan, in the island of Borneo, pos- 

 sesses the finest and largest diamond which has hitherto been discovered. It weighs 

 367 carats, and is said to be of the finest water. The celebrated Pitt Diamond weighs 

 only 127 carats. The Mattan Diamond is shaped like an egg, with an indented 

 hollow near the smaller end. It was discovered at Landak about ninety years ago ; 

 and though the possession of it has occasioned numerous wars, it has been about eighty 

 years in the possession of the Mattan family. Many years ago, the Governor of 

 Batavia sent a Mr Stewart to ascertain the weight, quality, and value of this Diamond, 

 and to endeavour to purchase it; and in this mission he was accompanied by the late 

 Sultan of Pontiana. After examining it, Mr Stewart offered 150,000 dollars for the 

 Diamond, the sum to which he was limited; and, in addition to this sum, two war- 

 brigs, with their guns and ammunition, together with a certain number of great guns, 

 and a quantity of powder and shot. The Rajah, however, refused to deprive his family 

 of so valuable an hereditary possession, to which the Malays attach the miraculous 

 power of curing all kinds of diseases, by moans of the water in which it is dipped, and 

 with which they imagine the fortune of the family is connected. 



GEOLOGY AND PHYSICAL GEOGRAPHY. 



InpiJdations or Mexico. — The Mexican Lakes are natural reservoirs, into which 

 the torrents, rushing from the surrounding mountains, deposit their waters. The 

 capital is situate in the centre of a valley, around which the encircling mountains rise 

 in successive stages, imtil they are lost in the distance. The city of Mexico occupies 

 the lowest part of the valley, and is scarcely more elevated than the level of the Lake 

 Tezcuco. Several lakes rise above each other, such as those of Xaltocan, Xochimiico, 

 Tzompango, and Chaleo, In consequence of the different elevations of these natural 

 reservoirs, the city of Mexico has for a long scries of ages been exposed to the ravages 

 of mighty inundations. The Lakes of Chaleo and of Xochimiico must necessarily 

 overflow their banks whenever a violent eruption of an adjoining volcano causes the 

 snows which cover its summit to melt. '* When I was at Guayaquil, on the borders 

 of the province of Quito, in 1802," says the Baron Al. De Humboldt, ** the cone of 

 Cotopaxi was heated by subterranean fire to such a degree, that, in a single night, it 

 lost the vast garment of snow with which it had long been covered." In the New 

 World, eruptions and great earthquakes are often followed by heavy showers, which 

 continue for several months. It may easily be imagined how dangerous the situation 

 of Mexico must be in a cHmate where, in the driest years, the rain falls to the depth 

 of 13 decimetres (about 59 inches). 



The inhabitants of New Spain think that these violent inundations follow each 

 other at neai-ly equal periods of time. Past experience seems to prove that a violent 

 eruption of the waters occurs every 25 years. Since the arrival of the Spaniards, 

 Alexico has experienced five very great inundations, in 1553, 1680, 1604, 1(J07, and 

 1629. In consequence of the opening of a canal, these evils were partially averted; 

 and since that time their effects have been less violent, occurring at intervals of 27, 24, 

 3, 26, 19, 27, 32, 25, 16, 24, and 23 years. These numbers do not follow each 

 other with so great a regularity as may be observed in the periods marking the re- 

 turns of the earthquakes at Lima, 



The situation of Mexico is rendered daily still more dangerous, by the circumstance 

 that the difference of level between the surface of the lake Tezcuco and the soil on 

 which the houses are constructed diminishes annually. This soil forms a fixed plane, 

 eepecially since the streets of Mexico were paved. The bottom of the lake of Tezcuco, 

 on the contrary, is continually elevated by the mud washed down by the surrounding 

 torrents. It was to avoid a similar danger that the Venetians turned from their 

 lagunes, the Brenta, Livenza, and other rivulets,* which form their alluvial deposits 

 within them. If wc could place much reliance upon the results of the levelling made 

 in the sixteenth century, there would be no doubt that the Plaza Mai/or^ oi Great 

 Square of IMexico, had formerly been elevated eleven decimetres (43 ^ inches) above 

 the level of the lake of Tezcuco, and that the mean level of the lake varies from year to 

 year. On the one hand, the moisture of the atmosphere has diminished by the de- 

 struction of the forests, and consequently the sources of the streams flowing from the 

 mountains which surround the valley have been lessened; but, on the other hand, 

 the clearing of the ground has increased the quantity of alluvial deposit, and the 

 rapidity of the inundations. General Andreossi, in his excellent work upon the Canal 

 of Languedoe, has explained these causes, which are the same under all climates. 

 The waters which glide over the declivities covered with a green sward, form less 

 alluvia] deposit than those which rush over the uncovered bank. This vegetable 

 covering, which may be formed either by the grasses, as in Europe, or by the httle 

 Alpine plants, as we find them in Mexico, can only be preserved under the shadow of 

 the forest. Again, the thickets and brushwood present obstacles to the waters which 

 roll down the declivity of the mountains, upon the molting of the snows. When these 

 declivities are destitute of vegetation, the rivulets of water are less retarded, they 

 unite more rapidly in torrents, and their deposits swell the lakes adjoining the city of 

 Mexico. 



Ascent of the Andes. — Don Juan de Ulloa, who went to Peru in compajiy with 

 the French academ.icians, to measure a degree of the meridian, gives the following 

 curious description of his ascent of the Andes : — 



"After many days saihng up the river Guayaquil, I ai-rived at Caracol, a town 

 situate at the foot of the Andes. Nothing can exceed the inconveniences we had 

 experienced in this voyage from the flies and mosquitoes. We were the whole day in 

 continual motion to keep them off, but at night our torments were excessive. Our gloves, 

 indeed, were some defence to our hands, but our faces were entirely exposed ; nor were 

 our clothes a sutBcient defence for the rest of our bodies, for the stings of these insects, 

 penetrating through the cloth, caused a very painful itching. One night, on coming 

 to onclior near a very handsome house that was uninhabited, we were no sooner seated 



• Andreossi sur le Canal du 5I:di, p. 19. 



in it than we were attacked on all sides by swarms of mosquitoes, so that it was impos- 

 sible to have one moment's quiet. Those who had covered themselves with clothes 

 made for this purpose found not the smallest defence; wherefore, hoping to find some 

 relief in the open fields, they ventured out, although in danger of suffering in a more 

 terrible manner from the serpents. But both places were equally obnoxious. On quitting 

 this inhospitable retreat, we took up our quarters, the next night, in a house that was 

 inhabited; the master of which being informed of the terrible manner we had passed 

 the preceding night, told us gravely that the house we so greatly complained of had 

 been forsaken on account of its being the purgatory of a soul ; but we had more 

 reason to believe that it was quitted on account of its being the purgatory of the body. 

 After having journeyed upwards of three days, througVi boggy roads, in which the mules 

 sank knee-deep at every step, we began at length to perceive an alteration in the cli- 

 mate ; and after having been long accustomed to heat, we now felt it grown very 

 sensibly colder. 



" It is remarkable that at Taraguagua we often see instances of the effects of two 

 opposite temperatures in two persons happening to meet ; one of them leaving the 

 plains below, and the other descending from the mountain. The former thinks the 

 cold so severe that he wraps himself up in all the garments he can procure, while the 

 latter finds the heat so great that he is scarcely able to bear any clothes whatever 

 The one thinks the water so eold that he avoids being sprinkled by it, the other is so 

 dehghted with its warmth that he uses it as a bath. 



*' The ruggcdness of the road from Taraguagua, leading up the mountain, is not 

 easily described. The declivity is so great, in some parts, that the mules can scarcely 

 keep their footing; and in others, the aclivity is equally difficult. The trouble of 

 sending people before to mend the road, the pain arising from the many falls and 

 bruises, and the being constantly wet to the skin, might be supported, were not these 

 inconveniences augmented by the sight of such frightful precipices and deep abysses, 

 as excite incessant terror. The road in some places is so steep, and yet so narrow, 

 that the mules are obliged to slide down, without making any use whatever of their 

 feet except as a support. On one side of the rider, in this situation, rises an eminence 

 of several hundred yards, and on ihv. other is an abyss of equal depth, so that, if he 

 should give the least check to his mule, and thus destroy the equilibrium, they must 

 both inevitably perish. 



'* Ilaviiig travelled nine days in this manner, slowly winding along the side of a 

 mountain, we began to find the whole country covered with a hoar frost, and a hut, 

 in which we reposed, had ice in it. At length, after a perilous journey of fifteen 

 days, we arrived upon the plain, at the extremity of which stands the city of Quito, 

 the capital of one of the most charming regions in the world. Here, in the centre 

 of the torrid zone, the heat is not only very tolerable, but in some places the cold 

 is even painful. Here the inhabitants enjoy all the temperature and advantages 

 of perpetual spring ; the fields being constantly covered with verdure, and ena- 

 melled with flowers of the most hvely colours. However, although this beau- 

 tiful region be more elevated than any other country in the world, and it took 

 up so many days of painful journey in the ascent, it is overlooked, neverthe- 

 less, by tremendous mountains — their sides covered with snow, while their sum- 

 raits arc flaming with volcanoes. These mountains seem piled one upon the other, 

 and rise to an astonishing height, with great coldness. However, at a deter- 

 mined point above the surface of the sea, the congelation is found at the same height 

 in all the mountains. Those parts which are not subject to a continual frost, have 

 here and there growing upon them a rush, resembling the Genista, or broom, but 

 much softer and more flexible. Toward the extremity of the part where the rusli 

 grows, and the cold begins to increase, is found a vegetable with a round bulbous 

 head, which, when dried, has an amazing elasticity. Higher still, the earth is entirely 

 bare of vegetation, and seems covered with eternal snow. The most remarkable of 

 the Andes are the mountains of Cotopaxi, Chimborazo, and Pichincha. On the top 

 of the latter was my station for measuring a degree of the meridian, where I suffered 

 particular hardships, from the intenseness of the cold, and the violence of the storms. 

 The sky around us, in general, was involved in thick fogs, which, when they cleared 

 away, and the clouds, by their gravity, moved nearer to the surface of the earth, ap- 

 peared surrounding the foot of the mountain, at a vast distance below, like a sea 

 encompassing an island in the midst of it. When this happened, the horrid noises of 

 tempests were heard from beneath, then discharging themselves on Quito and the 

 nei'^hbouring country. I saw the lightning issue from the clouds, and heard the thun- 

 ders roll far beneath me. All this time, while the tempest is raging below, the moun- 

 tain top where I was placed enjoyed a deUghtful serenity. The wind was abated, the sky 

 clear, and the enlivening rays of the sun moderated the severity of the cold. How- 

 ever this was of no very long duration ; for the wind returned with all its violence, and 

 with such velocity as to dazzle the sight, while my fears were incrc?-sed by the dread- 

 ful concussions of the precipice, and the fall of enormous rocks, the only sounds that 

 were heard in this frightful situation." 



Irish Bog. The moving bog on Lord O'Neill's estate, near Tlandalctopni, has 



chanf^ed its situation to a considerable extent. It has overspread the surrounding 

 land, and precipitated its mass into the river Maine, so as to obstruct the course of 

 the cm-rent, and lying in some places nearly twenty feet deep. 



METEOROLOGY. 



Dew-Butter. Tlie following singular fact is recorded in one of the first numbers 



of the Philosophical Transactions:— In the year 1695, during a great part of the 

 winter and spring, a fatty substance, somewhat like butter, was deposited by the at- 

 mosphere, instead of the usual dew, in Ireland, and particularly in the provinces of 

 Leinster and Munster. This substance is said to have been of a dark yellow colour, 

 and felt clammy, whence the natives called it Dew-butter. It fell in the course of the 

 ni"-ht on the moorish low grounds; and it was found in the morning attached to the 

 leaves of grass, to the thatches of houses, &c., in the form of pretty large lumps; 

 and it is added, that it seldom fell twice in the same place. It had an offensive smBll- 



