564 Progress in Science. [October, 



alight. So soon as the lamp is blown out, the bar begins to cool ; when quite 

 straight the catch is removed, liberating a spring which causes some matches 

 to be ignited and light a second wick. This lamp is especially applicable to 

 distant signal stations. Connected with the subject of light is the improved 

 Jet Photometer of the late Mr. G. Lowe for the estimation of the illuminating 

 power of coal-gas. It appears that when gas issues at a given pressure from 

 an orifice of constant size, the height of the flame varies directly as the 

 illuminating power of the gas. It amounts to the same thing if the height of 

 the flame be kept constant, while the pressure is varied, ensuring a more 

 delicate observation than could be made of the height of the flame. A table 

 has been prepared showing the value of the light for the variable pressure as 

 compared with the ordinary measure of sperm candles. 



Messrs. Bergius and Whyte contribute the solution of a very difficult 

 problem — the ascertaining of the depth of a marine sounding without any 

 reference to the length of line attached to the sinking weight. As the pressure 

 below the surface of the sea increases in proportion to the depth, means have 

 been taken to record this pressure. The sounding weight is hollow, and a 

 small tube communicating freely with the sea is carried nearly to the top of 

 the apparatus. The compression of the air begins in this tube; the water 

 soon rises to the top, and overflows into the chamber; there is no escape for 

 the water so entering, and the measure of its amount, by means of a scale, 

 shows the depth in fathoms to which the instrument has been sunk. 



Mr. F. S. Duckham exhibits a hydrostatic weighing machine, constructed on 

 the principle of the hydrostatic press, which will weigh up to 40 tons, though 

 itself no larger than an ordinary spring balance. The object to be weighed is 

 hung upon a piston, fitting in a small cylinder, and pressing upon the upper 

 surface of some water ; the amount of pressure, measured by a gauge, readily 

 gives the weight. 



Before leaving the building everyone passes to the enclosure in which 

 Mr. Hodgson's wire-tramway is at work ; this seems to be taking up and 

 delivering its loads as indefatigably as when on the Brighton Downs, where 

 the public first became acquainted with the results that can be achieved by 

 this invention. 



In this short notice it is impossible to enumerate all the improvements 

 exhibited; the endeavour has been to shoW that although many complaints 

 have arisen as to the paucity of scientific invention, they are certainly com- 

 bated by the consideration of the value of the exhibits. The admirable 

 reports of Professor T. M. Goodeve, M.A., Professor Abel, F.R.S., Lieutenant 

 T. English, R.E., and Henry Sandham, Esq., on the several branches of 

 science, will fully bear out this view. 



