X. TECHNOLOGY.--Cotton Seed Oil.--How cotton seed oil is made, and the cost and profits of the operation. 10335 Improved Dobby.--An improved weaving apparatus described and illustrated.--1 Illustration. 10333 Sulphur Mines in Sicily.--By Philip Carroll, U. S. Consul, Florence.--How sulphur is made in Sicily, percentage, composition of the ore, and full details. 10334 The Use of Ammonia as a Refrigerating Agent.--By Mr. T. B. Lightfoot, M.I.C.E.--An elaborate discussion of the theory and practice of ammonia refrigerating, including the hydrous and anhydrous systems, with conditions of economy. 10337 * * * * * INFLUENCE MACHINES.[1] [Footnote 1: Lecture delivered at the Royal Institution, April 27, 1888. For the above and for our illustrations we are indebted to _Engineering_.] BY MR. JAMES WIMSHURST. I have the honor this evening of addressing a few remarks to you upon the subject of influence machines, and the manner in which I propose to treat the subject is to state as shortly as possible, first, the historical portion, and afterward to point out the prominent characteristics of the later and the more commonly known machines. The diagrams upon the screen will assist the eye to the general form of the typical machines, but I fear that want of time will prevent me from explaining each of them. In 1762 Wilcke described a simple apparatus which produced electrical charges by influence, or induction, and following this the great Italian scientist Alexander Volta in 1775 gave the electrophorus the form which it retains to the present day. This apparatus may be viewed as containing the germ of the principle of all influence machines yet constructed. Another step in the development was the invention of the doubler by Bennet in 1786. He constructed metal plates which were thickly varnished, and were supported by insulating handles, and which were manipulated so as to increase a small initial charge. It may be better for me to here explain the process of building up an increased charge by electrical influence, for the same principle holds in all of the many forms of influence machines. This Volta electrophorus, and these three blackboards, will serve for the purpose. I first excite the electrophorus in the usual manner, and you see that it then influences a charge in its top plate; the charge in the resinous compound is known as negative, while the charge induced in its top plate is known as positive. I now show you by this electroscope that these charges are unlike in character. Both charges are, however, small, and Bennet used the following system to increase them.