Hertfordshire
a county of Engand the nebulæ and cluster of stars ob- land, bounded on the E. by Essex, on served by Messier and Mechain. In the 'S.. by Middlesex, on the W. by 1787, he discovered a 2d and 4th satellite Buckingham and Bedford, and on the of the Georgium Sidus, and in 1790 and N. by Cambridge. It has an area of 1799, five other satellites, viz., the 1st, 3d, 5th, and 6th. In 1781, George III. defrayed the expense of a 40-foot telescope. With this magnificent instrument Herschel discovered the 6th and 7th satellites, and also the spots, belts, and flattening on the four new planets between Mars and Jupiter. We owe to him also the discovery of invisible heat-