4 SCIENCE PROGRESS 



advantages at low speeds were not sufficient to counter- 

 balance the high cost of the large tyres employed, the in- 

 vention had been allowed to drop. The advent of the safety 

 bicycle, with small wheels to which springs could not easily 

 be attached, led Dunlop independently to discover and patent 

 the idea. 



Previous to the utilisation of rubber in the chemical labora- 

 tory, apparatus was connected, if possible, by means of glass 

 tubes bent twice at suitable angles. Occasionally one piece of 

 apparatus was ground to fit another. Otherwise, for such 

 purposes as connecting retorts with receivers, lutes were used. 

 Thomson says, in his System of Chemistry, sixth edition, 1820 : 

 " The lute most commonly used by chemists, when vessels are 

 exposed to heat, is fat lute, made by beating together in a 

 mortar fine clay and boiled linseed oil. . . . The accuracy of 

 chemical experiments depends almost entirely, in many cases, 

 upon securing the joinings properly with luting. The opera- 

 tion is always tedious ; and some practice is always necessary 

 before one can succeed in luting accurately." The lutes were 

 covered with strips of bladder or linen dipped in glue, made 

 fast with cord and allowed to dry before commencing the 

 experiment. It is not surprising that indiarubbcr was 

 adopted almost as soon as it became available. The use of 

 caoutchouc connecting-pieces was first described by Berzelius 

 in 1 814, in connection with his method of ultimate organic 

 analysis. He says : " I take a thin piece of [unvulcanised] 

 caoutchouc, and heat it a little. I bend it and cut off from 

 the bendings a small portion with a pair of scissors. The cut 

 surfaces unite together, and form a tube. If they do not unite, 

 let them be pressed with the nails against each other, taking 

 care not to touch them with the fingers." In his Chemical 

 Manipulation, 1827, Faraday remarks : " Caoutchouc connect- 

 ing pieces are easily made, and are of such constant use in 

 attaching tubes and apparatus for the conveyance of vapours 

 and gases, that a number of them, from an inch to two inches 

 long, and from a quarter to half an inch in diameter, should 

 be kept ready. . . . They are most easily made of the sheet 

 caoutchouc, prepared by Mr. Hancock, which is about the 

 tenth of an inch thick, and may be had in pieces ten or twelve 

 inches square. A piece of this caoutchouc about an inch 

 and a half square, is to be slightly warmed until it becomes 



