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Having now so fully described the microscope for viewing transparent objects, I shall very briefly notice that intended for opaque ones. It is represented in fig. 4, where A B is the great mirror, perforated in the centre for the purpose of admitting a cone of light proceeding from the lens D, and forming an image of a luminous aperture (not represented in the figure for want of space) just in front of the microscopic object O, situated in the focus of the metal. The attempt to construct this instrument was at first attended with a great deal of trouble, my original intention being to introduce a parallel beam of light, condensed by a combination of lenses, through a very small hole pierced in the centre of the metal. But for want of proper meclianical assistance the attempt proved abortive. I accordingly altered the plan, and enlarged the aperture to about 0.2, as in the figure, and admitted light through a bull's-eye. E, is a stop, to arrest the rays that would otherwise pass out to the eye-glass. It may be coloured according to the ground that is best adapted for displaying the object under observation.
After enlarging so fully upon the former instrument, it is not necessary to enter into much detail regarding the present one. All the observations upon the optical principle of the one apply with equal force to that of the other. I regret, however, that I had not an opportunity of ascertaining as satisfactorily by experiment the performance of this
' instrument, the perforated metal having been accidentally shattered to
fragments by afall. Some trials however, upon ordinary objects in ' its incomplete state, convinced me that this construction would perform well. It exhibited the brilliant scales of a curculio in a very pleasing manner. If upon the back of the stop E, a small silver cup be fixed so as to be turned round occasionally, it will enable us to vary the light by which objects are viewed; and to examine them at once by radiated and transmitted rays.
Nothing I conceive can be more simple than the optical principle of these instruments ; a single reflection, and a single refraction. And what on the other hand can be more complex than achromatic re-fractors with their triple, quadruple, quintuple, sextuple, and even tripletriple object glasses? As any ordinary reflector may be very simply converted into one upon the new construction for diaphanous objects, ‘by merely substituting a small diagonal metal for the Amician plane, I am not without hopes that some naturalist in possession of a standard
instrument will do me the honour of giving the new principle a fair '
trial. The result with an object metal wrought by a good artist,wil be decisive. I
‘ I have already extended this notice too far to enable me by this opportunity to communicate some speculations I intended upon several
new and curious achromatic combinations I have tried. I shall possibly do myself the honour of submitting them upon a future occasion ; mean,‘
>while, nothing Itrust has escaped me in the foregoing observations that can be construed into a disrespectful mention of the Amician
reflection. Far from me be the impertinence of disparaging an instru
'ment which the highest optical authorities have concurred to applaud.
I have merely ventured to inquire whether that instrument, superior as it is, has yet attained the maximum of excellence.
Notes relative to the collection of some Geological Specimens in the Kcisia Hills between Assam and Nunklow. By W. Cracroft, Esq. C. S.
On myjourney from Chira Poonjee to Assam, I endeavoured to recog~ nize the ascents and descents, and the geological features of the country, as laid down in Captain FIsHER’s Sketch, but I found this impracticable, excepting at those mountains of which he observed the altitudes. I was therefore led to‘ imagine that the intervals between the points given in his sketch had been filled in at random, and that the general geological characters of only the observed points were noted.
On my return, I endeavoured to obtain a nearer approximation to the real outline of the road, and the -positions of the various rocks, and I accordingly made the following notes of the time occupied in travel ‘ling, both in ascending and descending, the different hills, sketching their profile at the same time on the opposite page of my memorandum book, and noting the times and places at which the geological specimens already forwarded to you were collected. The heights of J yrong and other points I have taken from Captain FISHER, whose barometrical observations have been found to correspond very closely with others since made. Allowance has been made in the outline for the difference of time in ascending and descending. (See Pl. XX.)
First day, from 8h. 48m. ; commencement of ascent to Jyrong.
I began to ascend at viii. 48, through a narrow defile; the rock is apparently a fine grained granite, containing beds of A 2 (a conglomerate of iron clay) : at viii. 50, reached the bottom of the first descent, (which was a granite similar to No. 1, but rather whiter and less decomPosed) ; by xi. 7, I reached the next summit, the ascent yielding the granites, A. 4, 5, 6, and 7, and decomposing felspar: the road was then comparatively level till viii. 37, when the ascent became steeper and the rock all along was A. 8, (granite) ; but at 37 minutes containing large scales of mica (A. 9.)
The descent, after ix. 40, was at first very steep, with precipices at the road side : afterwards less steep; A. 10 and ll mica and gneiss being in
situ with red clay: the stream, passed at x. 57, runs over gneiss rock : at xi. 50, began to descend, and after passing a small stream, running over rock A 12, arrived at Jyrong at 12 o'clock ; the rock at Jyrong is A 13. The whole of this day's march was through a well wooded country. The gibbon or long-armed ape inhabits the forest near Jyrong, and its hootings echo through the forest ; wild elephants are occasionally seen and leopards. Second day, from Jyrong to Ongswye and Mopea.
The road continues through the forest, principally along the course of mountain torrents till vii. 33. where there is a level, capable of cultivation, and formerly was a stockade ; it is however a swampy place, and certainly not a good situation for a stage-house. If a stockade were erected at the top of the hill, which we reached at viii. 56., it would divide the journey from Mopea to Ranegang very equally, and much better than either Jyrong or Ongswye, the latter of which is situated in a hollow surrounded by a swamp. The decomposing felspar found at I. 25., and other places seems likely to afford porcelain. Asmall chesnut not much larger than a fine marrow-fat pea grows here; also a few
The view from Mopea is I think more beautiful than any on the road between Assam and that place.
Between Mopea and the Burpanee there is no jungle, the neighbouring hills have many fir trees. The water-fall at the Burpanee surpasses in beauty any I have seen ; it has not indeed the advantage of falling from a great height, but the body of water is very large : I descended with some difliculty to the rocks at the bottom of the fall, which seems not to be more than 80 or 90 feet, and is broken in several places; the black rocks, through which it has cut its passage, rise considerably higher than the stream, and overhang the basin at the bottom of the fall: they are well covered with wood. The basin extends to agreat distance, beyond which a turn of the river seems to inclose it, and gives it the appearance of a spacious lake. It is altogether truly sublime and beautiful. Between this river and the small stream at the bottom of the great ascent, the road winds through a forest of enormous fir trees; the mountain seems perfectly to overhang the road wherever you get a glimpse of it through the trees, and almost discourages the traveller from attempting the ascent, which occupies more than two hours.
An accident whichbefell me at Nunklow prevented the continuance of these remarks, but I collected a few specimens mentioned in the list, and
made the following observations in the neighbourhood of the Bogapanee and Kalapanee rivers.
At Mouflong the rock is white fiinty slate, the joints or strata. being nearly in the direction of the meridian and inclined to the horizon at an angle of about 60° ; this rock continues all the way down to the bed of Bogapanee river, which is covered with rolled masses of granite, gneiss, porphyry, and sandstone : wherever the rock bassets, it is red slate (E 2,) at the same angle and in the same direction as the white at Mouflong; immediately upon this lies a stratum of the conglomerate (E 3), containing pebbles of quartz and jasper with a talcose cement, of which large masses have fallen into the bed of the stream; it may be traced to the bed of the next nullah, where it also appears in sight ; the stratum above this is a dark sandstone, E 4, upon which is a stratum of basalt, or porphyry, F 5, the outside of which becomes red by decomposition. Above this are new sandstones of various hardness and colours (mostly white), alternating with conglomerate (E 6), which continue as far as the valley of the Kalapanee, in descending into which the same strata are visiblein the perpendicular face of the rock, and in the large masses which have fallen over ; E 7 (conglomerate) is picked out of a stream : about 80 feet above the stream, the same porphyry or greenstone basalt again appears, E 8, with veins of fine quartz E. 9. This rock forms the bed of the river, and continues till we begin to ascend on the opposite side of the valley (I saw one mass evidently columnar, the faces with angles of 120°). In the ascent we return to the sandstone, and conglomerate, in which I found a bed of lithomarge, E 10, anda bed of quartz conglomerate, containing crystals of amythystine quartz,
After reaching the summit on the road to the left leading to M0leem (at about 100 yards distance) is a bed of bituminous slate, E 12; from hence to Chira we meet only varieties of sandstone, with beds of stalslctitic iron ore, (No. 13), and of coal adjoining pipe-clay E 14, 15, which are found about a mile and a half south of Surareem.
Catalogue of Specimens, deposited in the As. Soc. Museum.
1. Fine grained granite, glassy and angular.
2. Conglomerate of iron ore with pebbles in beds in the above.
3. Granite resembling 1.
4. Do. apparently quartz in fine grains stratified with decomposing felspar, being No. 1, in a state of decomposition; but the rock No. 1, is regularly crystalline, its angles and joints perfectly defined. 0
5, 6. Fine grained red granite. (with minute crystals of hornblende ?)
7. Decomposing felspar with quartz in irregular fragments.
8. Fine grained red granite.
9. Gneiss‘ (granite stratified with plates of mica).
95. Conglomerate; iron ore and pebble found in a watercourse.
10. Decomposed gneiss,—pnrple.
ll. Decomposing felspar with quartz in very small particles.
'1l§ Quartz passing into gneiss; apparently a vein in the gneiss.
1. Black gneiss containing much hornblende.
Between Mopea and Nunklow, (marked C.) 1, 2, 3, 4, 5, 6. Granite, reddish and grey varieties—appr0aching sandstone. 7. A micaceous schist with red felspar. ' 9. Crystals of felspar decomposed, but retaining their form. 10. Mica stratified with decomposed felspar. 11. Mica in hexagonal plates. 12. Quartz tinged with mica. q 13. Micaceous, with crystals radiating from a point (approaching actinolite ?) 14. Red quartz (approaching hornstone) with mica. 15. Granite (the felspar decoznposed). 16, 17. Quartz with mica in veins.
Specimens, none Q/",them in situ, found on the ascent immediately below Nunklow.
1. Near Ly,yung, clay slate.
3. Slate, a small hill between the valley of King-lung-tung and Moufiong. Between Mvuflong and Surareem, marked E.
1. White sandstone. 8. Greenstone.
2. Red ditto ditto. 9, and 8. Fat quartz veins in No. 8.
3. Brescia. 10. Lithomarge.
4. Dark red sandstone (query old) ? 11. Coarse quartzy sandstone.
5. Basalt, conchoidal lumps. 12. Bituminous shale. I
6. Sand stone, new. 13. Stalactitic iron ore.
7. Clay slate. 14, 15. Coal.