everything is supposed to be perfectly smooth, the ratio ought to be independent of the magnitude of the sphere. In the imperfect theory of friction in which the friction of the fluid on the sphere is taken into account, while the equal and opposite friction of the sphere on the fluid is neglected, it is shown that the arc of oscillation is diminished, while the time of oscillation is sensibly the same as before. But when the tangential action of the sphere on the fluid, and the internal friction of the fluid itself are considered, it is clear that one consequence will be, to speak in a general way, that a portion of the fluid will be dragged along with the sphere. Thus the correction for the inertia of the fluid will be increased, since the same moving force has now to overcome the inertia of the fluid dragged along with the sphere, and not only, as in the former case, the inertia of the sphere itself, and of the fluid pushed away from before it, and drawn in behind it. Moreover the additional correction for inertia must depend, speaking approximately, on the surface of the sphere, whereas the first correction depended on its volume, and thus the effect of friction in altering the time of oscillation will be more conspicuous in the case of small, than in the case of large spheres, other circumstances being the same. The correction for inertia, when friction is taken into account, will not, however, depend solely on the magnitude of the sphere, but also on the time of oscillation. With a given sphere it will be greater for long, than for short oscillations.

Sixth Report of a Committee, consisting of H. E. STRICKLAND, Esq., Prof. DAUBENY, Prof. HENSLOW, and Prof. LINDLEY, appointed to continue their Experiments on the Vitality of Seeds.

THESE experiments have again been repeated upon 48 kinds of seeds gathered in 1843, as well as upon 26 kinds of new seeds added to the general collection in 1845.

Many kinds of old seeds, of various dates from 1812 to 1845 inclusive, consisting of 151 packets, have been contributed by Miss Molesworth. These were for the most part in small quantities, and were sown only at Oxford, on a slight hot-bed.

A small quantity of soil from the bed of a freshwater lake of the tertiary period, at Mundesley, Norfolk, containing scales of fish, elytra of beetles, seeds of Ceratophyllum and other plants from Sir W. C. Trevelyan, was subjected to three tests; viz. one-third part was placed in a shallow pan, and kept moist with distilled water; the second portion was kept well-saturated with the same; and the third portion, also in a shallow pan, under about one inch of distilled water. The whole was kept under a glass case to prevent the chance of seeds, &c. being deposited in it. No vegetation appeared in either case.

It may be well to remark, that the seeds have been sown under different circumstances, and have received different treatment at each of the three places they have been experimented upon. At Oxford, as in previous years, a selection was made from the whole quantity to be sown, of such as usually require the assistance of heat to enable them to germinate; these were sown in pots and placed in slight heat, and the remainder were sown on a small bed made in a cold frame, and, with the exception of two or three waterings, left to nature.

At Hitcham they were all sown in a border carefully prepared for them, and afterwards left to nature.

At Chiswick the whole of the seeds were sown in separate pots and placed in a pit heated with hot water.

These several treatments will at once account for the great difference there has been in many cases between the length of time the seeds required to vegetate, as well as the greater number of seeds which did vegetate at one place more than at the other, which will be seen on referring to the following statement of the results.

* At Hitcham, of 3 left, 2 did not flower, and the other produced no seed.

On the Colouring Matters of Madder. By Dr. SCHUNCK. THE organic colouring matters present such a wide field for inquiry, that it would require the labour of years to enable one person fully to elucidate their properties, or even to bring this department of organic chemistry into a state of development proportionate to the present condition of the science. The substances included under the name of colouring matters by no means agree in their chemical characteristics; they merely coincide in being possessed of certain vivid colours, or in giving rise to coloured compounds. Strictly considered, some of them ought to be classed among the resins and others among the extractive matters; and on the other hand, if we attempt a definition of the class according to their chemical characteristics, we shall find it impossible to exclude a large number of bodies, which, like tannin and catechin, are capable of giving rise under peculiar circumstances to brown substances, which in nowise differ in their general properties from the bright red colouring matters of archil, logwood, &c. Some colouring matters are presented to us ready formed in the different parts of plants and animals; others are produced artificially from colourless substances, which undergo very complex changes during the process; others arise spontaneously during the first stages of oxidation or putrefaction following the extinction of organic life. In the investigation of substances thus widely differing in properties and formation, it would be vain to expect at present anything approaching to general results in regard to the class as a whole. I must therefore content myself on this occasion with giving a short account of the results of some experiments which I have made on one branch of the subject, at the same time apologising for their present vague and undefined nature.

I have directed my attention in the first instance to madder, partly because the colouring matters contained in it are almost unknown, or rather worse than unknown, viz. known in such a manner as merely to mislead those who wish to inform themselves by the accounts given of them, and partly because madder is an article of such an immense importance in the art of dyeing that every discovery in relation to it acquires immediately a practical bearing.

It will be unnecessary for me to allude to the former numerous investiga