Cavallo

17.' A Treatise on Magnetism in Theory and Practice, 8vo. Load. 1787. Ed. 3. 1800. The ar rangement resembles that of the Treatise on Electri city : under the head of Theory the name of Alpi nus is mentioned with due respect. The original experiments are chiefly reprinted from the Philoso phical Transactions there is also a description of an improved mode of suspension for a magnetic needle, and there are several letters from Dr Lori mer on the terrestrial variation.

18. Of the Methods of manifesting the presence of small quantities of Electricity. Phil. Trans. 1788. p. 1. In this Bakerian lecture, Mr Cavallo-proposes an improvement on Volta's condenser, and makes some remarks on Mr Bennet's doubler, he thinks objectionable on account of the imponallitY to deprive the plate of a small quantity of electricity adhering to it. His own instrument has the advan tage of avoiding the friction to which th•condentell and doublers in their original form were liable.

19. Of the Temperament of musical intervals. Phil. Trans. 1788. p. 238. The author's particular ob ject is to calculate the exact scale for the division of a monochord, according to she system of a perfectly equal temperament : but he very candidly remarks, that " for playing solos," the usual temperament is the best, " giving the greatest effect to those con cords which occur most frequently;" and he oar, that when a haipifichord was tuned act ,rang to scale laid down on this monochord, the harmony perfectly equal throughout, and the effect "the same as if one played in the key of E natural on a harpsi chord toned in the usual manner." 20. Description of a new electrical Instrument, ca pable of collecting together a diffused quantity of Elec tricity. Phil. Trans. 1788, p. 255. This collector consists of a fixed plate of tin, situated between two moveable ones ; it is said to be more certain in its operation than the condenser, the results of which are liable to considerable irregolarities from various accidents, and to be more free from the inconveni ence of permanent electricity than the doubler.

21. Description of a Micrometer. Phil. Trans. 1791, p..288. Description and use of the Mother of Pearl Micrometer. five. Load. 1798. A thin slip of mother of pearl with a fine scale engraved on it, placed in the focus of the eye-piece of a telescope : its principal use is for ascertaining the distance of an object, of known dimensions, by its apparent magni tude thus measured ; for,instince, for judging of The distance of a body of troops, in military operations : the mother of pearl is found to be more convenient than glass for receiving the divisions, and to be suf ficiently transparent for transmitting the images of the respective objects.. •

• . the Multiplier of -Electricity. Nicholaon's Journal, I. p..894. 1797. In this letter Mr Cavallo attempts to show..the advantage of his instrument Over doublers; of .all kinds : Mr Nicholsoe, in a very respectful answer, expresses his doubts whether the objections to the doubler do not arise from its ex treme sensibility only, as demonstrating the existence of an electricity too weak to affect the other instru ments compared with it: Mr Cavallo had however remarked, that the inconvenience partly arose, from the greater intensity of the charge communicated to the plate of the doubler during the operation, which required a longer time for the restoratiqn of the na tural equilibrium.

• 23.

An Essay on the medicinal properties (factiti ous Airs, with an Appendix on the nature of the Blood. 8vo. London, 1798. The modern improvements in pneumatic chemistry have been still less productive of advantage to practical medicine, than the .dis covery of the powers of electricity, and this work can scarcely be considered as having• conferred any material benefit on the public. The observations on the blood are chiefly the result of a minute and care ful microscopical-examination of its particles, but the author was not particularly happy in the light which be employed for viewing them.

24. Elements of Natural or Experimental Philo iophy, 4 vols. 8vo. Loud. 1803. This work„ the last and most valuable of the author's publications, will long serve as a useful manual of the most important parts of the mechanical and physical The first volume is devoted to mathematical and practical mechanics; beginning with matter and motion, and proceeding to simple machines. The second relates, first, to fluids ; to the principles of hydrostatics, co hesion, hydraulics, pneumatics, sound, and music ; and secondly, to the most importantof che mistry. In the third volume we of heat, optics, electricity, and magnetism ; and the fourth, besides astronomy and the use of the glebes, contains a compendium of the history of aerosta tion; an account of meteors, including the recent dis. coveries respecting aeroliths ; and a collection of use ful tables.