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XVII. The Bakerian Lecture. — On the Gaseous State of Matter. 
By Thomas Andrews, M.D . , LL.B., F.B.S., Vice-President of Queen's College , Belfast. 
Received April 19, — Read April 27, 1876. 
§ 1 - 
Since the investigation “ On the Continuity of the Gaseous and Liquid States of Matter,” 
which formed the subject of the Bakerian Lecture for 1869, was communicated to the 
Society, I have continued to pursue the inquiry in a more extended form, with the view 
of discovering the general laws which determine the physical conditions of matter in the 
gaseous and liquid states. The subject in its whole extent and under all its aspects is 
so vast in itself, and its investigation in many cases has been surrounded by experimental 
difficulties of so high an order, that I must crave the indulgence of the Society if the 
amount of work actually accomplished appear small for the time devoted to it. I will 
give in the first place a few details regarding the method of mounting the apparatus, 
which will aid greatly any one who may hereafter desire to pursue the inquiry. 
The apparatus employed is, in all the essential parts, the same as that which I formerly 
described. The packing of the steel screw, by which the pressure is produced, is an 
important part of the operation. It is effected by means of a number of circular disks 
of leather, pierced centrally with a fine hole, and rendered impervious to water by being 
saturated in vacuo with melted lard. These disks are introduced, one by one, into a 
cylindrical cavity above the female screw in the lower end-piece, care being taken to 
press down each disk separately by a few gentle blows of a wooden mallet. After the 
introduction of the leather packing, the brass end-piece is placed with the face down- 
wards on a small wooden block, and the whole is firmly clamped to a steady bench or 
table. The steel screw is then inserted, and screwed through the leather packing till it 
enters into the wooden block. The connexion between the metal and glass tube in the 
upper end-piece is established by forming a protuberance on the glass tube accurately 
corresponding to a conical surface in the passage through the end-piece. The conical 
surface of the glass tube and the adjoining cylindrical surface for an inch and a half below 
the cone were covered with several layers of fine thread coated with ordinary shoemaker’s 
wax. The brass end-piece was gently heated before the introduction of the glass tube, 
and the latter was firmly fixed in its place by steady pressure. So perfectly have these 
arrangements fulfilled their purpose, that the apparatus, when successfully mounted, will 
remain in perfect order and without a trace of leakage for an indefinite period of time. 
The greatest pressure to which I have exposed the apparatus is 500 atmospheres, but it 
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