426 



EXHIBITION, BRITISH INDUSTRIAL. 



in their construction they presented nothing of 

 novelty, being but examples from the best ma- 

 kers which may be found described in Tredgold 

 and Bourne on the steam engine. 



GAS ENGINEERING. One of the best illustra- 

 tions of the progress effected since 1851 was 

 in the number of exhibitors of fireclay gas re- 

 torts at the Exhibition. This has been caused 

 through iron gas retorts being superseded by 

 earthenware retorts in almost every town ex- 

 ceeding 10,000 inhabitants. 



Mr. G. Glover, of Pimlico, exhibited a meter, 

 by which quantities of gas so minute as from 

 -pre to ^ oVe P ar t of a cubic foot can be measur- 

 ed with precision each second. 



Mr. Prossex exhibited his oxyhydrogen lime 

 lamp, the identical one used for three months 

 at the South Foreland lighthouse. 



In 1851 the only paraffine candle exhibited 

 was made from turf. The considerable display 

 made by Mr. Young, and Messrs. Field, and 

 many others, of blocks of paraffine and candles, 

 proves the manufacture of this article to have 

 arisen during the past ten years. 



Mr. Shepard's magneto-electric light was 

 shown. This remarkable light has been two 

 winters in use at the South Foreland lighthouse, 

 and is now fitted up by the Trinity Board at 

 Dungeness. The light produced is intense 

 sufficient, it is stated, in a revolving lens giving 

 off six rays, to enable any person with average 

 sight to read at a distance of ten miles. 



PHILOSOPHICAL INSTRUMENTS. Amongst the 

 general instruments exhibited were cloud mir- 

 rors, sunshine recorders; and a galactoscope 

 for measuring the transparency of milk. The 

 Right Hon. Robert Lowe showed spectacles 

 which magnify without glass or any other re- 

 fracting medium ; and Dr. Lankester exhibited 

 an ozonometer for registering the hourly varia- 

 tions of ozone. 



The improvements Mr. Wenham has effected 

 for microscopic objects deserve mention. No 

 longer a mere flat image is produced ; the bi- 

 nocular microscrope, by a contrivance for the 

 use of both eyes, gives perfect stereoscopic re- 

 lief, and at the same time saves much labor to 

 the eyes of the spectator. 



A machine was exhibited by Mr. Peters for 

 microscopic writing. The words to be written 

 microscopically are written in pencil, in ordi- 

 nary characters, on a sheet of paper at the bot- 

 tom of the instrument. But the pencil with 

 which this is done communicating by a series 

 of levers and gimbals with another minute pen- 

 cil and tablet at the top, is so graduated that a 

 stroke of a quarter of an inch at the bottom is 

 only a stroke of a quarter of a millionth of an 

 inch at the top, the shape and character of 

 both marks being nevertheless precisely alike 

 in outline. The object of the machine is chiefly 

 to irtark banknotes with certain minute signa- 

 tures for the prevention of forgery. Close by 

 this curious instrument was Mr. Babbage's 

 calculating machine, which will work quadra- 

 tiona and calculate logarithms up to seven 



places of figures. Messrs. Scheutz, of Stock- 

 holm, have improved upon it to such an extent 

 as not only enabled the machine to calculate its 

 tables, but to print its results.. This improve- 

 ment was at once bought up by the English 

 Government, but it is not now shown at the 

 Exhibition. 



Negretti and Zambra showed instruments en- 

 tirely new, and most of the important ones. 

 Among these was a thermometer so exquisitely 

 sensitive as to rise at once upon the approach 

 of the hand within two or three inches ; this 

 was made specially to test the temperature of 

 the body and coils of the python during her 

 attempted incubation at the Zoological Gar- 

 dens. 



M. Kcenig showed a wonderful collection of 

 instruments applied to the illustration of the 

 theory of the conduction, undulation, and vi- 

 bration of sound. By a most ingenious but 

 simple instrument a common glass cylinder, 

 coated with fine lampblack, and applied, turn- 

 ing, to a tuning key when vibrating M. Kcenig 

 makes sound its own printer. From the im- 

 pressions left on this cylinder all the different 

 vibrations and undulations of sound between A 

 and G are here recorded from their outset to 

 their latest tone, have been made to register 

 themselves, and from the records thus left a 

 most beautiful series of acoustic charts has 

 been drawn out. 



M. Perreaux exhibited a spherometer for 

 measuring the curves of object glasses. This 

 instrument is of such extreme delicacy, that 

 when adjusted to zero, even placing the hand 

 on the ground glass plane beneath, from which 

 the slender index works, is sufficient to deflect 

 it instantly. None in the foreign department 

 showed good photographic negatives of micro- 

 scopic objects but Roncoli, of Bergamo, in the 

 Italian section. Some of these instantaneous 

 photographs of the magnified blood and anato- 

 my of the most minute insects were among the 

 most wonderful tours de force that this chemi- 

 cal art showed in the building. In the French 

 department was the calculating machine of-M. 

 Thomas the Babbage of France. It is so 

 small as to fit in a compass not greater than 

 that of a good musical snuff box. Yet, by sim- 

 ply winding a handle, 18 seconds suffice to 

 multiply 8 figures by 8 ; to divide 16 figures by 

 8 figures only 24 seconds are required, and a 

 square root of 16 figures is obtained within a 

 minute! And all this is done by turning a 

 handle rapidly, and the price of the whole ap- 

 paratus is within the reach of most buyers. 



PHOTOGRAPHY AND PHOTOGRAPHIC APPARA- 

 TUS. Mr. Warren de la Rue exhibited his most 

 interesting series of photographs, showing the 

 progress of the late total eclipse of the sun as 

 seen in Spain. 



Col. Sir Henry James, director of the ord- 

 nance survey, showed specimens of "photo- 

 zincography/' for the reduction, enlarging, and 

 printing of maps and plans. Sir Henry showed 

 adaptations of it to the production of facsimiles 



