318 Progress of Invention. 



bearing were only used as a motive power and then released ; that 

 the levels being always attached would not run the risk of any jar 

 in handling and placing on the pivots ; and that he thought if the 

 telescope described a true vertical curve the form of the joints was 

 not so important as generally supposed, although he could still test 

 them if necessary. The principal nse of the instrument would be 

 for obtaining the longitudes of the different stations of the survey 

 (of which an arc of 10 degrees was now waiting for their deter- 

 mination) by electric telegraph signals, and the transit would remain 

 one or two months at each station. 



PROGRESS OF ESTVENTION. 



ISTew Method of Cementation. — In certain experiments made 

 by M. L. Cailletet he found that cast iron, by long exposure to a 

 temperature less than that which causes fusion, loses an amount of 

 carbon which renders it very similar in constitution to steel. It 

 differs, however, considerably from the latter, since it is forged 

 with difficulty, and the bars obtained from it are incapable of being 

 tempered. It is very brittle, and when broken resembles some 

 kinds of oxide of manganese. Pursuing these researches further, 

 he discovered that when bars of iron are heated for about twenty 

 hours to a temperature somewhat under that at which gold melts, in 

 contact with granulated grey cast iron, which has been carefully freed 

 from all fatty matters and any adhering carbonaceous substances, 

 in boxes from which the air is excluded, they are converted into 

 steel of very good quality. They must be in contact with the cast 

 iron, since, as was proved by experiment, their conversion is not 

 due to the gases of the furnace having entered the boxes, those not 

 in contact with the cast iron not being converted. This discovery 

 is capable of being applied to a very practical purpose, since, if 

 engraved and polished plates of wrought iron are used instead of 

 the bars, they are cemented without suffering the least distortion, 

 or even having their surface tarnished. Neither are blisters or 

 other imperfections, so usual when steel is cemented with carbon, 

 produced upon them. 



Mode op Rendering "Wood Plastic. — A new and very simple 

 method of effecting this has been lately discovered. It consists in 

 forcing dilute hydrochloric acid through the cells of the wood, at a 

 pressure of about two atmospheres. This impregnation must be 

 continued for a length of time, dependent on the nature of the 

 wood. The bark is not previously removed, and by a very 

 simple arrangement the fluid is introduced at one end of the 

 log, and passes out at the other. If while the wood is 

 still wet it is exposed to pressure, the cells having been 

 first washed out with water, its volume may be reduced to a tenth 

 of what it was originally ; the fibres being brought into the closest 

 contact, without being fractured or torn ; and when dry they have 

 no tendency to separate again. If it is pressed in dies, their details 



