Cavallo

3. An account of some new Experiments in • Phil. Trans. 1736, p. 1S. Consisting, of re marks en Professor Lichenberg's discovery of the peculiarity of the figures exhibited by strewing powders on the cake of the eleotnephorue; with. an account of two improved• electroutetera, 6; Thermanietrical Experiments and Obtervaliont, Phil. Trans. 175% p. 585.. This was w Bakeritin lecture, delivered by appointseentof tho.Presithult an• Council of the Royal Society; an appointment which entitles the lecturer to a small fee,, lett by the will of Mr' Henry Baker, bet, which is. commonly considered as rather complimentary than lucrative, These experiments relate to the abet produced by colouring the- bath. of a thermometer' eapesed to the sun's rays, and to the intensity of heat at different distances from its source. The most refrangible colours appeared to absorb the most heat ; and it was observed that even the day-light, without sun shine, occasioned a perceptible difference in the in dications of the different thermometers.

7. An Essay on Medical Electricity, 8vo, Lon don, 1780. It is seldom that persons not medical have been sufficiently incredulous in their opinions respecting the operations of remedies ; and the whole of the expectation held out in this work, has cer tainly not been fulfilled by later experience ; but, as a candid and distinct relation of cases, it may still have its value.

8. .4ccount of a Luminous Appearance. Phil. Trans. 1781, p. 829. One of the permanent arches since found to be connected with the aurora borea lis. It was so bright that the stars could not be seen through it, and lasted about an hour.

9. Thermonsetrical Experiments. Phil. Trans. 1781, p: 509. A Bakerian lecture, relating to the evaporation of ether, to the expansion of mercury, and to a thermometrical barometer ; that is, a very delicate thermometer, for ascertaining the tempera ture of boiling water at different heights above the level of the.sea, according to the idea then suggest ed by Sir George Shuckburgh, and very lately re sumed by other natural philosophers. Mr Cavallo observes that the instrument has the advantage of being- very portable ; but that unless the quantity of water be considerable, its boiling temperature will be somewhat unsteady.

10. A Treatise on the Air and other Permanently 'Elastic Fluids. 4to, Lend. 1781. This elaborate work commences with the principles of chemistry and of hydrostatics, and proceeds to relate all the known properties Of the different kinds of elastic fluids, many of which had been very lately discover ed ; these are followed by an account of some origi nal experiments, for example, on the gas produced by the deflagration of gunpowder, which is found to be chiefly nitrogen and carbonic acid, without any nitric oxyd ; on the explosion. of hydrogen mixed with atmospheric air, and on the evolution of gas from plants, respecting which the author finds some reason to differ from the opinions of Dr Ingenhurz.

Considering that Mr Cavendish had not then dis covered the composition of the nitric acid, it must be allowed that the experiments on gunpowder may justly be deemed an important step in the progress of chemical Science. .

- 11.

Descriptioneye an Improved Air Pump. Trans. 1783, p. 435. The improvement was made by Ham and Hurter, and consisted in a mode of opening the valve of oiled silk mechanically, when the elasticity of the air became too weak to raise it. The rarefaction obtained went to about the thou sandth of an atmosphere : in this state the air trans mitted eleetricity, with a light equably diffused ; and the balls of the electrometer exhibited no divergence. Some later improvements are • said to have carried the rarefaction to 12. Description•ef a Meteor. Phil. Trans. 1784, p. 108. This observation was made at Windsor, and is highly valuable, from the circumstance of a noise like thunder having been heard, about ten mi mites after the explosion of the meteor was seen; hence the author concludes that its direct distance was 130 miles,• and its height 56i.

13. The History and Practice of fErostation, 8vo, Lond. A work of temporary rather than of per. manent interest ; but which it was the more na tural for Mr Cavallo to undertake, as he was one of the first who had made experiments on the mesas of employing hydrogen for raising bodies into the air by its levity.

14. Mineralogical Tables. f. Explanation. 8vo, Load. 1783 ; containing a comparison of the differ ent systems of mineralogical arrangement then mat generally adopted, but at present almost wholly al. perseded by later methods.

15, 16. Magnetical Experiments and Observations. Phil. Trans. 1786, p. 62 ; 6. Two Bake. rian lectures ; the former relates chiefly to the mag netism of brass, and of some other metals, generally rendered discoverable by hammering them ; in the latter, the same subject is continued ; and it is shows that the same powers may be detected in the metal; in question without hammering them, if they are placed on a very clean and wide surface of quick silver. The limit, at which red hot iron begin to be attracted by a magnet, is found to be the heat at which it ceases to be visible in the day-light. A considerable change is observed in the .magnetic powers of iron during its solution in acids: and the author endeavours to apply these experiments to the explanation of the variation of terrestrial mop netism, as derived from the effects of heat, and from internal changes in the constitution of the earth. Mr Bennet has endeavoured to explain the pheno mena observed by Mr Cavallo, from the accidental operation of foreign causes, but he has not been per fectly successful in the attempt.