JOLLY BALANCE. 275 JOMMELLI. the fixed point will be opposite some higher divi- sion on the scale, which, of course, is noted. Weights are then added to stretch the spring the same amount. The difference between the weights required to stretch the spring from its zero point to where it rests when the body is weighed in the air, and the amount required to bring it to the position it assumes when the pan and bodj' are in the water, divided into the total weight, gives the specific grav- ity. The usual arrangement of the apparatus is to have two pans, the lower of which is kept sub- merged in the water so that the conditions remain constant whether the body is placed in the upper or lower pan. The etched mirror usually employed forms an admirable scale, inas- much as it enables the observer to avoid parallax and deter- mine accurately the position of the fixed point, as when the bead or other point on the spring is seen with the eye, re- flected together in the mirror, it implies that the eye, the fixed point, and the scale division are all in a straight line perpen- dicular to the surface of the mirror. In an accurate deter- mination correction should be made for the temperature of the water, as explained under Specific Gravity, and the wire which carries the lower pan sliould be as fine as possible to eliminate the effects of capil- larity between the water and the wire. The Jolly balance is used mostly for rapid determination of specific gravity of such objects as mineralogical specimens, and does not admit of as great precision as an analyt- ical balance arranged for specific-gravity deter- minations. The spring must be suited to the weights of the objects which are to be used, so that the extensions will not be produced over too long or too short a range of scale. In the latter case a small error of observation will seriously affect the result. See Specific Gba^ity. JOLLY-BOAT (joUi/, from Dan. jolle, Swed. jiille. Dutch jol, Eng. t/aid + hoat). A small boat similar to a working dingy (see Bo.t), but generally smaller and broader. It is of cut- ter model, with a square stern, and usually clinker-built. The term is now^ little used, but a boat of this character is nearly always carried by merchant vessels. JOLOF. See YoLOF. JOLY, zh6Te', Henbi (1839-). A French philosopher. He was bom at Auxerre : studied at the Ecole Xormale Superieure: and taught at Douai until 1S71. and then at Dijon, where he was made dean in 1S78. He was assistant at the Sorbonne (1881-8.3), and taught for a year (1886-87) at the Coll&ge de France. After the suppression of his chair there he returned to JOLLY BiLASCE. Dijon. His works include: Psychologie com- paree (1877) ; Psychologie des graiules homtnes (1883) ; Le crime (1888) ; La France criminella (18S9); La morale (18S0); Socialisme chretien (1892); and Malebranche (1901). JOMABD, zho'mar', Edme Feaxqois (1777- 1S62). A French Egyptologist, born at Ver- sailles. He studied at the Ecole Polytechnique, and accompanied the French army to Egypt in 1798 as a member of the scientific commission. Returning in 1802, he was appointed secretary to the commission, and in this capacity he edit- ed the great Description de I'Egypte, contributing many essays, which were later published sepa- rately, and directing the printing for twenty years. In 1821 he took part in founding the Geographical Society of Paris, and in 1828 he be- came conservateur administrateur in the Koyal Library. He suggested to ilehemet Ali to send a number of young Egyptians to be educated in Paris under his direction, thus forming the so- called Institut des Egypt iens. The next Viceroy conferred upon him the title of Bey. He wrote, among other works: Voyage a I'Oasis de Hyouah ( 1823) ; Remarques sur les rapports de VEthiopie et I'Egypte (1822). JOMINI, zho'me'ne', Hexei, Baron (1779- 1809). A French general and writer on military topics. He was bom at Payerne, in the Canton of Vaud, Switzerland, and began his military career in a Swiss regiment in the French service, becoming secretary of the Department of War under ilassena in 1799. He left the army in ISOl, and in 1805 began the publication of his Traite des grandes operations militaires, and in the same year entered the French Army, becoming chief of staff to Marshal Xey. He was present at Ulm (180.5) and at Jena (1800), participated in the Prussian campaign of 1807, and was sent to Spain in the following year as chief of staff to ^Marshal Xey. He served in the Russian cam- paign of 1812 under Berthier, and did good ser- vice during the retreat. In 1813 he helped win the battle of Bautzen; but, offended at the treat- ment which he received from Xapoleon. he passed over to the Allies and entered the service of Alex- ander of Russia. He refiised, however, to fight against France or to divulge the military plans of Xapoleon, which were well known to him. In 1828 he took an active part in the military operations at Varna, and in 1855 settled at Brussels. Jo- mini was a magnificent tactician and strategist, on the field as well as in council. Besides the work already mentioned, his Eistoire critique et militaire des campagnes de la Revolution (Paris, 1820-24). his Vie politique et militaire de Na- poleon (Paris, 1827), and his Tableau analytique des principales comhinaisons de la guerre (Saint Petersburg. 1830) are of great value to the mili- tary student. Consult Lecomte, Le general Jomini <3d ed.. Lausanne, 1888). JOMMELLI, yo-melle, Xicol6 (1714-74). A famous Xeapolitan composer, and one of the most celebrated masters of his time. He was bom at Aversa. near Naples, and was educated under Canon llozzillo. Durante. Fee. Leo. Prato. and Mancini. Previous to his appointment as kapell- meister to the Duke of Wiirttemberg. in 1754. his music had been marked by every characteristic of his national school, and as such was very popu- lar with his countrymen ; but the influence of German ideals during his stav in that country
