mountains, described described as having rectilinear spouts at the top, and which, from the description, I take to be a kind of cirrus.* Other clouds appeared at the time, which, by the account, appear to have been dense cumulostrati and cumuli. As irregularities in the electric state of the air may be concerned in the production of many disorders of health, the investigation of them becomes additionally interesting. It is much to be wished, that those who have opportunities of making experiments with electrical kites, &c. would attend to what is the general disposition of the clouds, which prevail during different states of the atmospheric Electricity. An instrument likely to throw some light on this subject has been invented by M. de Luc, described in the next section.

* Clouds of this kind, attaching themselves to the tops of high hills and mountains are noticed by Saussure as being called les nuages parasites; and considered as portending Rain. Refer to Saussure, Voyage dans les Alpes, § 2070, and M. Du Carla in Journal de Physique for 1784. Homer. Iliad. v. 522. Theophrastus, De. Sign. Temp., and Aratus, Dios. 188.

SECTION VII.

Of M. De Luc's Aerial Electroscope, and the Connexion observed between its Action and other Atmospheric Phaenomena.*

Ir may not be improper to present the reader with a short account of M. De Luc's Electric Column, or Aërial Electroscope, as this instrument has been frequently alluded to in my Journals.

It is composed of a great number of small circular and very thin plates, about the diameter of a sixpenny piece of silver, of paper and of zinc, alternately arranged, forming a column; the two ends of which are made to approximate, and at each of them is attached a small bell; a metallic clapper is then hung between them, and the whole apparatus is insulated by being fixed on glass stands. One end of the column is observed to become electrified plus, as it is termed, and the other minus; consequently, one of the bells becomes electrified plus, or positive,

* See Letters of M. De Luc on this Column in many numbers of Phil. Journal, and in Phil. Mag. the present month, Oct. 1814, p. 248.

and the other minus or negative: and the metallic clapper moving rapidly from one to the other, to equalize the two electricities, a pulsation is produced, and the bells ring. Neither the heat or cold, dryness or moisture of the atmosphere, appear to have any considerable influence on the action of this instrument; but it is considerably altered by peculiarities in the electric state of the atmosphere. The prevalence of cirri ramifying about the sky in various directions, and accompanied often by other modifications, by dry easterly and changable winds, and by numerous small meteors of an evening which appear to indicate a disturbance in the atmospherical Electricity, I have noticed to be accompanied by an irregular action of the Electric Column of M. De Luc; the bells ring at intervals, and with a kind of hurried pulsation. When such weather as I have described is followed by Rain, the bells have been found silent. There are also other varieties in the kind of pulsation of the bells; sometimes they ring weak and regular, sometimes weak and irregular, sometimes strong and regular, at others strong but irregular; the intervals of quiescence are sometimes of longer duration than at others. These minute variations are probably connected with peculiarities in the

state of the atmosphere, as I have said above, which are worthy attention, because they may be principally concerned in producing many disorders of health which are attributed to atmospheric influence: when the weather is settled, when only diurnal cumuli prevail with Westerly Winds, then the action of De Luc's column is the most regular; and this is found to be the most wholesome kind of weather.*

Since the publication of the first edition of this book, I have seen the superb columns made by M. De Luc, himself. The varieties of the action seem to correspond with my own observations on the instrument belonging to M. Benjamin M. Forster, of Walthamstow, which continued ringing with varied action for a year, and which received the whimsical appellation of the Perpetual Motion, or the Jubilee Bells, because they happened to begin to ring on the Anniversary so called in honour of the 50th year of the Reign of the late King.

M. Benjamin M. Forster has lately discovered another very curious fact, which shows the connexion between Electricity, Galvanism, and Magnetism, an instrument to demonstrate which he has already described.

* See Phil. Mag. June and July, 1811.

CHAPTER VIII.

FURTHER INVESTIGATION OF PECULIARITIES OF WEATHER.

If it can be shown, as above, that there are varieties in the state of the atmosphere, with which the prevalence of disease seems conjoined, so that the said diseases may be referred to its agency, analogy would lead us to ascribe other diseases, for which no particular cause could be assigned, to some other peculiarity in the air, which, however, might not be demonstrable by any meteorological instruments: and our inquiries will be directed to discover in what such peculiarities may consist. I have already shown that the peculiarities of weather alluded to as being accompanied by the great prevalence of disorders, do not appear to consist in the dampness, dryness, heat, cold, levity, or gravity of the atmosphere, nor in the combination of any two or more of these, or any other qualities of the air, demonstrable by meteorological instruments; but that, in many instances, they appear to be marked by the peculiar character and