350 



ANNUAL REGISTER, 1794 



pint of it in that state; it was giveti 

 to me by M. d', ircet, to whom some 

 had been sent from the Isle of 

 France. It was kept several win- 

 ters in a room without a fire : but 

 after the hard frosts of I788-9, I 

 found the bottle broke. I think it 

 may be useful to take notice of this 

 accident, as the like, most proba- 

 bly, has not been recorded. I am 

 not able to point out, either at what 

 degree of temperature the decom- 

 posed liquor passed to the solid state, 

 or in what manner it crystallised ; 

 because I did not go into the place 

 where it was kept until the weather 

 had become much milder. 



The difficulty of procuring the 

 juice unaltered m this country is evi- 

 dent ; ar.d the distance of the places 

 where the trees grow ; the necessity 

 of having agents there to see the 

 necessary articles properly executed; 

 the length of lime we should be ob- 

 liged to wait before we could re- 

 ceive what was ordered , all concur 

 to render it an object of desire both 

 to philosophers and artists, ti.at tliey 

 might be able to use the bottles of 

 caoutchouc, which we have here in 

 abundance, so as to make from them 

 the various instruments they may 

 have occasion for. Many persons 

 have employed themselves in this 

 research, but I know not that as yet 

 any one has succeeded. 



It was soon discovered, that it 

 was not possible to employ liquefac- 

 lion by means of heat; caoutchouc 

 indeed melt^ as eaiily as otherresins, 

 but when cooled it remains liquid 

 and adhesive. Alcohol, or spirits 

 of wine, the usual solvents of resi- 

 nous substances, did not act upon it, 

 nor was it dissolved in water, as 

 gums are, It was then tried to dis- 

 solve it in drving oils, and it was 

 found that by the aid of heat the 



caoutchouc was dissolved, and foririJ 

 ed an excellent varnish, supple, im- 

 pervious to air or water, and resist- 

 ing a long time the action of acids. 

 With this varnish Messrs. Charles 

 and Robert covered their balloons ; 

 and an ingenious artist, M. Bernard, 

 and afterwards thir brothers Durand, 

 made with it several instruments 

 useful in surgery. Their catheters 

 are much used, and are kncwn by 

 the name of catheters of elastic 

 gi-m ; they are flexib'e and have a 

 sulhcient elasticity ; they are, how- 

 ever, nothing but taffety, covered 

 with a solution of clastic gum in 

 some kind of drying oil. This 

 coverirrjjafrersome time cracks, and 

 falls off in scales, and they then be- 

 come unserviceable. They have 

 not the property of lengthening, 

 and again recovering their former 

 dimensions, like a tube of caout- 

 chouc : perhaps there may be cases 

 where, for this very reason, these 

 .instrun:!er.ts may be preferable to 

 those which might be made of the 

 pure elastic gum. 



Macquer also made some re- 

 searches on this subject, and to hira 

 I believe it was first known that 

 ether dissolves caoutchouc without 

 altering its nature. He proposed to 

 appl the solution, layer upon layer, 

 on a mould, and to let the ether 

 evaporate ; this process was how- 

 ever too long, and too expensive, 

 to be of much use : moreover the 

 very fact of the dissolution has been 

 contested by many chymist^', who 

 have not succeeded in repeating the 

 experiments of Macquer ; respec- 

 ting which, thtre is not at present 

 any manner of doubt, although it is 

 not yet determined whence arose the 

 different results in theexperiments of 

 those who were occupied on this sub- 

 ject. A well-known fact, the publicar- 



lion 



