nt subject of preservation of sight. 10341

VI. MECHANICAL ENGINEERING.--Economy Trials of a
Non-condensing Steam Engine.--By Mr. P. W. Winans,
M.I.C.E.--Interesting notes on testing steam engines. 10331

The Mechanical Equivalent of Heat.--By Prof. De Volson
Wood.--A review of Mr. Hanssen's recent paper, with
interesting discussion of the problem. 10331

VII. METEOROLOGY.--The Meteorological Station on Mt. Santis.--A
new observatory recently erected in Switzerland, at an
elevation of 8,202 feet above the sea.--1 illustration. 10341

VIII. NAVAL ENGINEERING.--Improved Screw Propeller.--Mr. B.
Dickinson's new propeller.--Its form and peculiarities and
results.--4 illustrations. 10333

IX. PHOTOGRAPHY.--Manufacture of Photographic Sensitive
Plates.--Description of a factory recently erected for
manufacturing dry plates.--The arrangement of rooms,
machinery, and process.--10 illustrations. 10336

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