AND OF THE PHYSICAL SCIENCES. 



63 



from four to sis inches; the appendage being from two to three inches long; the toes 

 somewhat approximate, accurainate — the inner being shorter than the outer one. 

 Step from eif^hteen to twenty-five inches. Found in the south-west part of Montague ; 

 also at Horse Race. 



0. teiradacfi/his. Fig. 1. — Length of the foot, exclusive of the hind toe, from 

 two and a half to three and a half inches. Toes divaricate ; the hind one turned in- 

 ward so as to be nearly in the line of the outer toe, prolonged backward. A space, 

 however, usually remains, between the heel and the hind toe, as if the insertion wero 

 hio-her on the leg than the other toes, and its direction obliquely downwards. Length 

 of the step ten or twelve inches. 



O.palmatus. Fig. 2. — Four-toed, all directed forward; the fourth toe being short, 

 proceeding from the inner part of the foot; the heel is broad; foot from two and a 

 half to three inches long. Length of step eight inches. Discovered at Horse Race. 

 0. minimus. Fig. 3. — "With three widely-spreading toes, nearly of equal length ; 

 feet measui-ing from half an inch to an inch and a half long ; step from three to five 

 inches. 



On comparing the descriptions which we have given of the species, it is interesting 

 to observe how the length of the step increases in proportion to the size of the foot ; 

 from the ivgens, having a foot sixteen inches in length, with a stride at least four feet, 

 to the minimus^ whose foot-print is but one inch long, and its step from three to five 

 inches, which are indicated in the three specimens given in our first cut, drawn to a com- 

 parative scale. All these tracks appear to have been made on the margin of shallow 

 water that was subject to changes of level, and in which sediments of sand and raud 

 were alternately deposited. And the length of the legs, which must be inferred from 

 rtie distance of the foot-prints from each other, was well adapted for wading in such 

 situations. 



The sandstone in this valley, where the Ornithichnites occur, extends nearly one 

 hundred miles from New Haven, in Connecticut, to the north line of IMassachusetts, 

 varying in width from eight to twenty-four miles. It is divided by one or two ridges 

 of greenstone, protruded through the sandstone, and running nearly north and south. 

 The strata of the sandstone have a general easterly dip, varying from 5 to 30 de- 

 grees ; so that the lowest or oldest portions of the sandstone lie along the western 

 side of the valley. These lower strata consist, for the most part, of thick layers of 

 red sandstone, not much diversified in appearance. But the upper strata, that is, 

 those on the easterly side of the greenstone ranges, consist of slaty sandstones, red 

 and gray conglomerated sandstones, very coarse conglomerates, shale, and perhaps 

 red marl, with occasional beds of fetid limestone. Indeed, the red sandstone of 

 Hartford is decidedly marly, as it effervesces with acids, and even contains nume- 

 rous veins of calcspar. 



The important discovery of the gigantic foot-prints of the Ornithichnite, which 

 we have first described, is a further proof that there were animals inhabiting the 

 former world of much larger dimensions than any existing races. The Mammoth 

 maybe mentioned as the largest of quadrupeds ; and the 0. giganteus seems to have 

 been the largest of birds. In Professor Hitchcock's '* Report on the Geology of 

 Massachusetts," published some time ago, he shows that other organic beings, that 

 must have been contemporaries with these immense birds, were their compeers in 

 size ; for we find in that work a description of a Sea- Fan (Gorgonia Jacksoni), 

 found in the new red sandstone of West Springfield, that has been uncovered, with- 

 out reaching its limits, eighteen feet in length, and four feet in width ! Indeed, the 

 colossal bulk of these birds is in accordance with the early history of organic life in 

 every part of our globe. The much higher temperature that then prevailed seems 

 to have been favourable to a gigantic development of every form of life. 



METEOROLOGY. 



On the Meteorology of the Neighbourhood of Edinburgh. — The diffusion 

 of heat and moisture over the surface of the earth is a subject full of interest ; but it has 

 not yet received that strict attention which its importance demands. We still require a 

 great many local facts and observations to enable us to form general and correct con- 

 clusions. The regular prevalence of the equatorial currents, by which a stream of 

 hot and moist air is constantly ascending from the earth's surface, and passing by 

 various modifications to both poles, from whence a drier and colder current flows to- 

 wards the equator, to occupy the place of the other, seems to be the grand agency 

 employed by nature to warm, and refresh with moisture, every region of the globe. 

 With our insular situation and temperate latitude, these currents are not so constant 

 or so distinctly marked; yet even here we can trace them generally prevailing. 



Thus, for eight months in the year, we have either south-west or west winds al- 

 most constantly prevailing ; while, for the other four months, we have either east or 

 north winds, alternating with north-west and south-west winds. 



During our summer and autumn months, the tropical current blows very generally 

 from the southwards : the great summer heat of the northern continent of Europe, 

 by rarifying the air in that direction, causes a current to blow towards it. 



This effect is sometimes retarded and interrupted by causes that diminish the heat 

 of the continent — such as long and severe winter snows, and the late thawing of ice. 

 Under these circumstances, we have moist and cold summer weather. 



In winter, the low arctic current, blowing towards the tropics, occasionally has 

 the ascendancy, especially when the sun is in the southern ecliptic. And, in spring, 

 an easterly wind prevails generally for six or eight weeks, till the continental land 

 becomes heated, and then the east mnd yields to the supremacy of the south and 

 south-west. 



With these general principles the local phenomena in the atmosphere in this nei"-h- 

 bourhood appear to coincide. And the differences of temperature and moisture be- 

 tween the east and west coasts of Scotland seem very marked. 



To-day the summit of Arthur's Seat is enveloped in a dense cloud of vapour, the 

 vrind blowing from the southward. This cloud is stationary, and has been so for the 

 last hoar; nor does the vapour pass many yards beyond the mountain. The cause 

 of this phenomenon is well understood: the current of wind is loaded with vapour, 

 suspended in it by its high temperature. The temperatur« of Arthur's Seat is con- 



siderably lower: whenever a portion of this current, then, comes in contact with the 

 hill, it is suddenly cooled, deposits its vapour, and each successive portion of the 

 current does the same. The mist does not extend beyond the hill, because the con- 

 densing cold is no longer present, and any remaining portions of deposited vapour 

 carried along into the general mass are instantly redissolved. 



More diffused fogs are not uncommon in this neighbourhood, especially in the 

 spring months, when there happen to be two currents of air in the atmosphere. An 

 east wind prevails annually here for the greater part of the months of April and May, 

 usually setting in about the middle of April, and continuing, more or less, till the end 

 of May. Blowing over the long tract of north-eastern continent, it is exceedingly 

 chill and deficient in moisture. When it arrives on our insular shores, it gains an 

 accession of temperature, and, with this, its capacity for absorbing moisture is prodi- 

 giously increased. This accounts for its chilling and arid effect on the whole veget- 

 able and animal creation, and on the face of the soil generally; it greedily abstracts 

 both their heat and moisture. A cold current of wind, thus sweeping along, and meet- 

 ing with a warmer mass loaded with moisture, suddenly causes a deposition of vapour; 

 but this cold current is so close to the surface of the earth as to prevent the usual 

 formation of rain — a dense fog usually is the result. 



These adverse currents were very perceptible in June 1832, and they appeared not 

 only to cause fogs, but also several tremendous thunder-storms. 



For some time previous to the 1st of June, the wind had prevailed from the east. 

 On the 1st and 2d of June, an atmospheric current, passing from south-west to north 

 east, was distinctly indicated by the rapid and continued motions of the clouds in 

 that direction, at a moderate height in the air. On the 3d, the wind was still from 

 the east — the atmosphere was remarkably transparent, and there was a dry scorching 

 heat. In the evening, a dense fog from the eastward suddenly came on, whii;h 

 quickly passed into rain; and, on the morning of the 4th, at seven a.m., loud peals of 

 thunder were heard, accompanied by vivid flashes of lightning. For eight days after- 

 wards the weather continued chill, foggy, and rainy, with wind east-north-east. On 

 the I3th, the weather became milder, the lower stratum of air blew from the eastward, 

 while, above, dense masses of nimbi were seen rolling from south-west to north-east. 

 At seven p.m., a tremendous thunder-storm came on, passing directly over the city 

 from the south-east to north-east. In several cases the report followed the vivid flash 

 instantaneously, with a sharp piercing sound. The electric fluid struck two different 

 parts of the city, doing partial injury. We had then mild cloudy weather, with 

 wind south-west, till the 20th. The morning of that day was clear and cloudless — 

 wind unsteady, easterly; at twelve noon, a thunder-storm in the west passed distantly 

 to the northward of the city. A dense thunder cloud appeared in the western hori- 

 zon, arched, and tolerably well defined above, while below it was ragged, and con- 

 stantly joined by numerous accessory clouds. A deep flame-coloured lurid light 

 occupied the whole circular space, from the cloud to the horizon ; and the dark 

 accessory clouds shooting along this space, to join the main cloud, had a singular and 

 highly interesting appearance. This lurid light frequently accompanies thunder 

 clouds; whether it be caused by the electric matter, or is the effect of a modifica- 

 tion of the sun's light falling on these clouds, is uncertain. A tortuous mass of 

 clouds, something like a tornado, and producing similar effects, is said to have been 

 witnessed to the westward of Edinburgh during this thunder-storm. After this 

 storm, the weather continued throughout the month steadv and genial. That these 

 different currents of the atmosphere were connected with the electric phenomena 

 just mentioned, tht-re is every reason for supposing. Most probably, the higher 

 current of heated air, moving from the south, and saturated with aqueous vapour, 

 was positively electrified, and thus coming in contact with the cold, dry, and nega- 

 tively electrified cast wind, would be suddenly condensed, and an equiUbrium of the 

 electric fluid would be effected. 



Thunder-storms, of any great magnitude, have been rather rare in this neighbourhood 

 for the five years preceding 1831. In June of that year, two violent storms passed 

 over this city. The night previous to the first great storm, flashes of diffused sheet 

 lightning irradiated the heavens for upwards of an hour, accompanied by low peals of 

 thunder. Next morning was calm and serene, but exceedingly sultry. About two 

 p.ji,, thick masses of clouds began to rise from south-west, and float along the ridge 

 of the Pentland Hills. Gradually the dense mass accumulated over the city — vivid 

 flashes of forked lightning, succeeded instantaneously by a loud report, occurred at short 

 intervals, and rain descended in torrents. The peculiar lurid glare was very con- 

 spicuous to the north-eastward, as the storm gradually passed in that direction. Al- 

 though the hghtmng thus flashed almost close to the tall spires and houses of the city, 

 yet no injury was done. A vessel, however, was struck in Leith Roads, a situation 

 lower by several hundred feet, and her masts were shattered to pieces. That the 

 ' lightning did not strike on the higher and exposed parts of the city is wonderful; 

 and, indeed, it is remarkable how very rarely such accidents occur in large towns, 

 while they arc so frequent in the open country, and especially where there are trees 

 and water. It, perhaps, may be accounted for thus — that the air overhanging cities 

 is highly rarified from the numerous fires, is free from moistui-e, and, consequently, 

 can act but as a very imperfect conductor of electricity. 



Since 1831, we have annually, about May, June, and July, experienced several 

 severe thunder-storms. In all of these which we have witnessed in this locality, the 

 clouds first make their appearance in dense masses to the southwards, coming along 

 either in the direction of the Lammermoor or Pentland Hills, while the sky to the 

 east and north is generally cloudless and transparent. These electric clouds, becoming 

 larger and denser as they proceed, pass onwards with a slow motion to the north or 

 east. 



The exposure of Edinburghshire, on the eastern coast of Scotland, renders it pe- 

 cuharly subject to easterly winds. On the more inland parts of the country, and 

 especially on the west coast, these winds are not so severely felt ; for the space of 

 country which they blow over in their progress serves to mitigate their severity. The 

 cUmate on the eastern coast, however, is less liable to excess of humidity. The an- 

 nual average fall of rain is, at Dalkeith, twenty -five inches — Edinburgh, twenty-three ; 

 while at Largs, near Glasgow, it is forty-three and a half inches; at Dumfries, thirty- 

 sis; at Castle Toward, Argyleshire, fifty inches. This, too, is easily accounted for 



