Though the genus Lepidophloios, in regard to species, is a comparatively small one, yet it derives considerable importance from its occurring throughout the whole of the Carboniferous Formation, as well as in the peculiar characteristics of the plants comprised in it.

The fragmentary condition in which the specimens are usually found has given rise to the creation of several genera, which can all be shown to merely represent different conditions of growth and preservation of one generic type. There are, also, other points in the structure of Lepidophloios which require further investigation, and the object of the present paper is to attempt to clear up some of these, about which much confusion still exists.

The Coal Measures of the South Wales Coal Field fall into three well-marked divisions:—

I. The Upper Pennant or Upper Penllergare Series.

II. The Lower Pennant Series.

III. The White Ash Series.

In 1885 I paid a visit to this Coal Field, with the object of studying its Fossil Flora, hoping by this means to ascertain the relative position of the Welsh Coal Measures to those of the other Coal Fields of Britain.

In all languages where there exists a certain amount of intellectual culture, manifesting itself in the oral or written form of what is called Literature, there must always coexist with it an inferior stratum or platform of speech; the platform of common colloquial intercourse of the mass of the people, and specially of the peasantry and lower classes. The necessity of this bistratification arises from the diverse class of ideas, and the diverse style of intercourse, pervading the two platforms. Language is a growth that flows from the intercommunion of associated persons working out, within a certain bounded circle, the vocal expression which their ideas, their energies, and their circumstances demand for the purpose of common action.

In the two papers previously communicated to this Society under the above title, Parts I. and II., I have given the results of my observations on the dust in the atmosphere for the years 1889 and 1890. In this paper will be given the results of similar observations I have been able to make during the years 1891, 1892 and 1893. The observations made during these last three years are similar to those made in the two previous ones; and were mostly made at the same places and at about the same dates as those already given. These five sets of observations are therefore comparable with each other, and give a fair statement of the number of dust particles in the atmosphere at the different places at the particular dates.

The chemical examination of ground-air, i.e., the air which is contained in the pores of the soil, was first made by Boussingault and Levy in 1853. Their results, however, attracted little attention till Pettenkofer, in 1857, pointed out that the determination of the amount of carbonic acid in the air of a given soil might be used as a means of estimating the organic decomposition going on there. In 1871 he first published his results, and since that time the subject has been worked at by many investigators both from the agricultural and hygienic point of view, including in the latter class Fleck at Dresden, Eodor at Buda-Pesth, Hesse in Saxony, and Nicholls in America. As researches of this nature have not attracted much attention in this country, a short account of the modus operandi may be interesting as a preliminary.