It will be seen, from this short mention of the several varieties of equatorial mountings, that I give a most decided preference to the general form or principles of construction of the German instrument, in which preference it cannot be supposed that there is any undue element of partiality, as none of the forms are of my own devising. The British Association, it will be recollected, long since impressed with the importance to science of having a powerful instrument sent to a southern latitude, urged the British Government to contribute to the work, and appointed a committee to examine and select the most effective form of instrument, &c. &c. Anxious to be a successful competitor in such an undertaking, I applied myself to remove the only apparent objection to the German form of instrument, and also to devise such modification of its details as would suit it pre-eminently for a large reflecting telescope. Both these objects were accomplished with entire success. My plan, as also estimates, had the honour of being approved of by the Committee before referred to; and although it would now appear as if, from some occult cause, the distinction of being the constructor of the proposed instrument is likely to remain an honorary one, still, as the improvements spoken of are applicable to instruments of much smaller dimensions, it may not be unprofitable to lay the general principles and results of these before the Association.

That which the German form of equatorial seemed alone to require, was a system of equipoise inter se, unobjectionable in itself, and which would reduce the nature of the pressures of the declination axis on its bearings to the same which these would be if the polar axis were vertical instead of inclined to the co-latitude of the observatory. The declination axis of a large instrument of the German type has necessarily great diameter, and its bearings, if ground in to fit without shake, as they may be in a small instrument, would have too much friction; it is therefore desirable that the bearings should be in effect Ys, and in order that such bearings shall be as admissible as in a meridional instrument, the pressure of the axis on each side of its Y bearing should be equal in every position of the instrument; moreover, it is desirable that the end pressure of the declination axis, in all positions of the instrument out of the meridian, shall be neutralized. These important conditions are perfectly fulfilled by a system of internal counterpoise, which, being applied, then permits of an external system of anti-friction rollers, relieving the Y bearings of all but a fractional portion of the remaining pressure of the declination axis and its appendages (viz. the telescope and its counterpoise). The result of such arrangement may be readily anticipated; an achromatic telescope of 12 inches aperture and 20 feet focus, so mounted and with perfect steadiness, is moved by a force of about one pound applied at the eye end.

Secondly, and for the equatorial mounting of the largest reflecting instruments up to 6 feet diameter (the size of Lord Rosse's), if required, I modify the German type, as shown in the drawings exhibited, by placing the declination axis within instead of beyond the larger end of the polar, and I invert the whole. Thus the previous steadiness is rather increased; the bearings of the polar axis may both be of minimum size, and the centre of gravity of the whole instrument is brought as close to the ground-level as can be desired, instead of being considerably aloft; also, the settings and readings of the largest instrument are rendered most convenient, and the observer is generally close to the ground, and never more than a few feet from it.

The subjoined Table contrasts the weights to be moved and power required for the same, in the second English and improved German forms of equatorials, for telescopes of several sizes, viz.

In respect to the foregoing Table, it is right to state, that, so far as Nos. 1 and 2 are concerned, the data in columns C and D are the results of calculation; and the same is to be understood of column D in the case of No. 3. The data for No. 5 are taken directly from those of No. 3, while the numbers appended to No. 6 give the result of actual experience.

Report on the Experimental Plots in the Botanical Garden of the Royal Agricultural College at Cirencester. By JAMES BUCKMAN, F.L.S., F.A.S., F.G.S., Sc., Professor of Geology and Botany, Lecturer on Geology, &c. at the Cheltenham Proprietary College.

THE experimental plots in the garden of the Royal Agricultural College rest partly on a thin bed of forest marble clay and partly on the brashy soil of the underlying Great Oolite, so that, although most of the soil is of a heavy tenacious character, still a large portion is that of the porous Stonebrashes so prevalent in the district, the nature of the geology being readily made out from the following section.

a. Forest Marble Clay.

b. White Freestones of the Great Oolite.

Neither the staple of the land itself, nor any method of cultivation that has as yet been adopted renders this part of the Royal Agricultural College Farm better, if indeed equal, to the land of the best part of the farm; so that the agricultural experiments at least are not likely to suffer in value from being carried on too exclusively under the conditions of garden culture.

The garden is for the most part divided into plots, the greater portion of which are 24 yards square-many however are double that size, whilst small borders are occupied with single specimens of flowering plants, the latter being mostly grown for assisting demonstrations in the lecture room.

With merely agricultural experiments, the method I have adopted is to first use a small plot, and then adopt either a 5-yard plot or four of these united, after which the matter is transferred to the farm; so that as time progresses, and facilities for carrying on these experiments increase, it is hoped that this garden may be the means of introducing new and valuable varieties of crops to the farmer, as well as of elucidating some interesting facts and principles in Botanical science.

The plots for the present year, 1857, are employed in the growth of plants in the following groups :

1. THE GRASSES.-These may be very conveniently divided into the following groups.

a. Grasses of value in meadow and pasture.

b. Grasses which are but pasture or agrarian weeds.

c. Grasses which indicate certain conditions of soil, climate, &c.

As regards the plots of grasses generally, I may state that last year these consisted to a great extent of two sets, one planted five years before, and a new lot now just coming to perfection, the difficulty of keeping species unmixed, and other circumstances attendant upon growing specimens in small plots, rendering frequent renewal absolutely necessary. As respects the purity of a crop, the older beds offered some most interesting observations, as they show how in a short period one species may be entirely lost, and the ground be taken possession of by others; hence the following:

Three beds, side by side, have become mixed in the following manner.

Observations of this nature are interesting in a practical point of view, as, from cultivation or the want of it, meadows are constantly changing their contents, good grasses gaining the ascendant in the former, and bad in the latter. In my plots, bad grasses, that is those of a poor feeding quality, take possession of plots originally sown with better kinds; this arises from the circumstance of the general poverty of the soil, which is assisted by these crops never being depastured like those of meadows, but on the contrary are left to perfect themselves for the teaching of the students, and consequently are annually cut down as ripened or seeded grasses, thus affording a practical example of the injury arising from exhausting crops, besides showing that

*These and most of the older beds have this year been occupied by totally different crops, the old crops of grasses being gradually destroyed.

many of the grasses only maintain a perfectly perennial habit by being cropped off before they have seeded. This consummation having been attained, many species, such as the Loliums, Hordeums, Dactylis, and Alopecurus, die out the same, or at best the second year afterwards; and indeed in cultivation, even when cut before it is ripe, the old plants gradually die out.

Grasses indeed differ so much in the species that prevail and the well or ill doing of these according to circumstances, that the practical observer of them, either in a wild or cultivated shape, or, better, both, may become acquainted not only with the broad features connected with the conditions of soil, but all their inflections, such as its value, the cultivation it has experienced or that should be adopted, mechanical texture, want of draining, and the like.

As regards particular Botanical facts that have received illustration from my experiments, I would shortly comment upon the following genera:Alopecurus, Dactylis, Agrostis, Poa, Festuca and Bromus*. Of the first two genera, I received packets of seed from the seedsman with the following

The A. nigricans I take to be but a variety of A. pratensis; and indeed, after three years of growth, it may almost be pronounced as identical. Both do well; and I can see no reason for preferring the one to the other, so alike are they in growth and habit.

As regards the two names of Dactylis, for they are nothing more, they are here inserted to note with reprehension a practice too often adopted by seedsmen, of giving a new name from some accidental enlargement of form perhaps arising from suitable soil-or other unimportant distinctions; and thus disappointment results to the cultivator, while works are burdened with synonyms.

Agrostis. The last year's plots of this were as under :

Plot A. Agrostis vulgaris.

Plot B. Agrostis stolonifera.

These were sown in 1855, and at the last meeting they presented the following appearances :

A. "Presents the usual delicate A. vulgaris of the grass meadows with a few plants of A. stolonifera intermixed."

B. "The general plant is A. vulgaris having a few A. stolonifera intermixed; and these latter present more of the A. alba form than of the congested inflorescence and true stolon growth of the A. stolonifera."

This seems to favour the view that the three forms are all referable to a single speciest, as when cultivated in a like position their broader features of distinction are lost, and the seed of one, though for the most part coming true, will still send up exceptional examples of each of the others; but the diversity of conditions under which the three forms occur in nature seems sufficient to account for the different aspect which they assume, such asA. vulgaris, common to upland meadows.

A. alba, in ditches and damp places.

A. stolonifera, in stony brashes, mostly an accompaniment of agrarian conditions.

*Avena and Ægilops to be noticed in the Cereal list.

†This is more strongly confirmed in the present year, 1857, as now

Plot A is attaining the size and appearance of A. alba.

Plot B is nearly all A. alba. These plots are on a thin clay bed.

POA. Of this genus, among other species the two following were sown side by side.

P. aquatica (Glyceria).

P. fluitans (Glyceria).

These were sown in the autumn of 1855. During 1856 stiff and sturdy short-and rigid-leaved plants were forming; these leaves were so harsh as to cut the flesh on the slightest touch. During the present year, 1857, they have flowered, and to my utter astonishment the plants of both plots are the same; the culms were as much as a yard in height, and the flowers so small and ovate as quite to justify the retaining of the generic name of Poa for the whole group.

While these grasses were flowering, I watched them from day to day with great interest, as in all their parts they differed so much from any known species; the short rigid leaves with the angular sheath, and the elegant panicle of flowers from their size, and the rigidity of the whole plant removed these far from the P. pratensis, and the whole details differed so much from the forms whose seed was sown as well as from all other recognised forms, that while it showed me I could not have mistaken my sced, it also was convincing that I had obtained a new and singular variety. This indeed is not to be wondered at when we consider that both the forms, the aquatica and fluitans, absolutely grow in the water; but here I had got them to grow in an upland situation, and to manage like other upland grasses with only water from rain. Still the change was so curious, that I was anxious to re-examine the seeds as sown; and fortunately some of the packets were saved, and I can pronounce them true as named*.

Here then I cannot help concluding that even such dissimilar grasses as the typical forms of P. aquatica and P. fluitans are not specifically distinct; and though the former in its wild state bears a large and diffuse panicle of flowers, and the latter is almost as spicate as a Lolium, yet we may, I think, connect the evidence here presented to us with that obtained in the growth of the Festuca loliacea pratensis and elatior presently to be detailed.

However, I shall not conclude my experiments upon this subject without sowing some new plots with seeds of the hitherto supposed species gathered by myself for the express purpose; not that I in the least doubt these experiments, but in order, if possible, to note the changes more clearly †. FESTUCA. The species to be communicated upon I shall divide into two groups.

a. Festuca ovina.

a. These were sown six years since in three distinct plots, and they soon established themselves in a separate tufted method of growth. The first two years they were readily distinguishable; now, however, the following facts are observable.

F. ovina is about eighteen inches high; F. tenuifolia, duriuscula and rubra differ but slightly in size, and scarcely in details, and the creeping habit of root of the latter is entirely lost.

It may be remarked that the F. rubra is not amongst our wild forms at Cirencester, but I have occasionally met with specimens of F. duriuscala in

*The two packets were sent for examination.

+ Specimens of the new Poas are sent for examination.

Certainly not so much as regards the width and length of the leaves, as the same form takes on in bushes when compared with the open ground.