23G report — 1859. 



On a Deep-sea Pressure Gauge. By Henry Johnson. 



The pressure gauge ma}% in its present form, be considered as a small hydraulic 

 press ; of which the ram is forced into the cylinder by the increasing pressure of the 

 sea when sinking, and expelled by the expansion of the water in the cylinder when 

 rising. 



It consists of a small tube or cylinder having at one end a tap, through which 

 water is admitted ; the tap having in addition to the passage admitting water, a 

 smaller passage for the escape of air. At the other end of the cylinder is a packing 

 box, through which a round bolt or solid piston passes. A scale by the side of the 

 piston contains the degrees of compression, and an index at the further end of the 

 scale is drawn along the scale by the piston when forced by increasing pressure into 

 the cylinder, and secured in its position by a spring taking hold on a toothed rack 

 at the side of the scale, where it remains when the piston is pushed back by expan- 

 sion of water in the cylinder to its former position. 



The scale and index are protected by a tube screwed on to the cylinder, and the 

 cylinder is protected from the risk of indentation by an outer tube. 



In an experimental instrument the packing-box has remained water-tight under 

 the application of a pressure of 400 lbs. to the square inch on the piston ; so that 

 the isolation may be considered sufficiently perfect, as in actual use this pressure on 

 water in the cylinder would be counterbalanced by the external pressure of the ocean. 



As the amount of friction required to obtain this isolation is considerable, and 

 may be affected by the screwing down the packing-box, it w r ould be desirable that 

 after any alteration of the packing-box the instrument should be suspended, and the 

 amount of friction ascertained, by hanging on to the piston a weight sufficient to 

 overcome the friction. 



In ascertaining the pressure of water, the amount of friction overcome should be 

 added to the compression indicated by the index, to obtain the total amount of 

 pressure. 



Some portion of the diminution of bulk will probably be occasioned by variation 

 of temperature, and which causes a greater variation in bulk at high temperature — 



As 4000 parts of sea- water at the temperature of 86° Fahr., 



contracted to 3986 parts at the temperalure of 65°, being jJ$o parts for 21°. 



While from the temperature of 65° to 35°, the diminution 



to 3977 parts was only at the rate of ?T ' W parts for 30°. 



The contraction of the cylinder by variation of temperature counteracts the varia- 

 tion of water to a very small extent, being about T „Vo ta P arts f° r 40 ° Fahr. 



On Surface Condensation. By J. P. Joule, LL.D., F.R.S. 



The author described the experiments he had made on this important subject. 

 A peculiar arrangement he had introduced gave a very increased effect to a given 

 surface. In this arrangement a copper spiral was placed in the water spaces. The 

 spiral had the effect of giving the water a rotatory motion, and the water was thus 

 compelled to travel over a larger surface than it otherwise would do. 



On a Submarine Lamp. By Mr. Kettie. 



The principle on which the lamp is constructed and depends for action, is that 

 arising from the discrepancy of the gravity of the two columns of air necessarily 

 engaged, viz. the column of cold for supplying combustion, and the column of heated 

 air ejected ; and in the arrangement of the tubes, advantage is taken to foster the 

 peculiar qualities of the respective columns ; thus the cold being made to descend by 

 the larger and outer tube, whose surface is exposed to the action of the water; while 

 the heated or centre column is placed immediately over the powerful burner of the 

 lamp. 



The lamp may be made either of a globular or cylindrical form, the bottom being 

 made of brass, with a large screwed opening for the admission of the Argand burner 

 used ; on the top of the globe is a brass cap, into which is screwed a strong copper' 



