CANE SUGAR. 



2. Thermo- Electric Pyrometers. If wires of two dissimilar metals be in 

 contact at their ends, and if the temperature of the two ends be different, an 

 electric current flows along the wire, and its voltage or E.M.F. is a function 

 of the temperature difference between the heated and cold ends : this arrange- 

 ment is called a thermo-electric couple, and by simply measuring the E.M.F. 

 thus obtained, the temperature at the hot end follows. For high temperature 

 work the thermo couple is made of platinum and rhodium, and will indicate 

 correctly temperatures up to 2900 F. 



3. Radiation Pyrometers. In this instrument the rays of radiant heat 

 emitted from a hot body are brought to a focus by a suitable combination of 

 lenses and arc directed upon the junction of a thermo-electric couple. From the 

 E.M.F. or voltage the temperature is directly obtained. 



4. Optical Pyrometers. The optical pyrometer of Wanner is based on the 

 colour produced by incandescent bodies : its theory is rather complicated. 

 Externally the instrument closely resembles a polariscope, and it is used in a 

 very similar way, being directed towards the body whose temperature is being 

 determined : the critical appearance of the field of vision thus observed and 

 the means of obtaining it are very similar to those used in polarimetry. 



Of these instruments the first three can be provided with a continuous 

 recording device. The electric pyrometers are perhaps not suitable for the 

 very high temperatures of the combustion chamber ; this is chiefly due to the 

 difficulty in protecting the platinum wire or the couple from the action of the 

 furnace gases. The combination arranged by the Cambridge (England) 

 Scientific Instrument Co. recommends a Fery radiation pyrometer for deter- 

 mining the temperature of combustion, and a thermo-electric couple for the 

 flue gas and feed- water temperatures. A complete outfit costs less than 100, 

 and in a factory of any size should quickly pay for itself. 



Megass as a paper making Material. Attention was first 

 called to this possibility in Guadeloupe in 1872, and it has been frequently 

 suggested during the last few years. Amongst the large amount of irresponsible 

 matter that has been written the following definite statements have appeared : 



It has been stated that megass owing to its length of fibre yields a very 

 good half stuff wrapping paper, there being a yield of 48 per cent, of half 

 stuff from megass. The failure of experiments in Java is stated to be due to 

 local conditions and not to the quality of the raw material. Thiele 11 has given 

 a description of the results obtained with diffusion megass in a factory in 

 Texas; the crude material contained 82 per cent, water, 16*5 per cent, crude 

 cellulose, '75 per cent, carbohydrates and '75 per cent, ash of which 82*77 

 per cent, was silica ; the megass was allowed to ferment in heaps with frequent 

 watering whereby the pectins were destroyed; a charge of 40,0001bs. of 

 fermented megass was boiled in a * rotary ' for four hours under a steam 



424 



