Fire balls of the size of goose eggs, composed of coal and charcoal in powder, mixed up with a due proportion of wet clay, and well dried, would make a much more cleanly, and in all respects a pleasanter fire than can be made with crude coals; and I believe would not be more expensive fuel. In Flanders and in several parts of Germany, and particular in the Dutchies of Juliers and Bergen, where coals are used as fuel, the coals are always prepared before they are used, by pounding them to a powder, and mixing them up with an equal weight of clay, and sufficient quantity of water to form the whole into a mass which is kneaded together and formed into cakes; which cakes are afterwards well dried and kept in a dry place for use. And it has been found by long experience that the expense attending this preparation is amply repaid by the improvement of the fuel. The coals, thus mixed with the clay, not only burn longer, but give much more heat than when they are burnt in their crude state. It will doubtless appear extraordinary to those who have not considered the subject with some attention, that the quantity of heat produced in the combustion of any quantity of coals should be increased by mixing the coals with clay, which is certainly an incombustible body;--but the phenomenon may, I think, be explained in a satisfactory manner. The heat generated in the combustion of any small particle of coal existing under two distinct forms, namely, in that which is COMBINED with the flame and smoke which rise from the fire, and which if means are not found to stop it, goes off immediately by the Chimney and is lost,--and the RADIANT HEAT which is sent off from the fire, in all directions in right lines:--I think it reasonable to conclude, that the particles of clay which are surrounded on all sides by the flame arrest a part at least of the combined heat, and prevent its escape; and this combined heat, so arrested, heating the clay red hot, is retained in it, and being changed by this operation to radiant heat, is afterwards emitted, and may be directed, and employed to useful purposes. In composing fire balls, I think it probable that a certain proportion of chaff--of straw cut very fine, or even saw dust, might be employed with great advantage. I wish those who have leisure would turn their thoughts to this subject, for I am persuaded that very important improvements would result from a thorough investigation of it. CONTENTS of ESSAY V. A SHORT ACCOUNT of SEVERAL PUBLIC INSTITUTIONS Lately formed in Bavaria. together with the APPENDIX to the FIRST VOLUME. Account I A Short Account of the military academy at munich Account II An account of the means used to improve the bread of horses, and horned cattle, in Bavaria and the Palatinate. Account III An account of the measures adopted for putting an end to usury at Munich.