APPENDIX. 



" be no occasion for luting, as the tube a£ts like a funnel 

 " in carrying off the vapour. 



" When tlie water begins to boil, the vapour fhould 

 *' be allowed to pafs freely for a minute, which will 

 " effedually clean the tube and upper part of the boiler. 

 " The tube is afterwards to be kept conftantly wet, by 

 *' paffing a mop or fwab, dipped in fea-water, along its 

 " upper furface. The wafte water running from the mop, 

 ** may be carried off by means of a board, made like a 

 " fpout, and placed beneath the tube. 



" The diftillation may be continued till three fourths of 

 " the water be drawn off, and no further. This may be 

 " afcertained cither by a gauge-rod put into the boiler, 

 " or by meafuring the water diflilled. The brine is then 

 " to be let out. 



" Water may be diflilled in the fame manner while the 



219 



n 



provifions are boiling. 



" When the tube is made on (liore, the beft fubftance 

 " for the purpofe is thin copper well tinned, this being 

 *' more durable in long voyages than tin plates. 



*' Inftead of mopping, the tube, if required, may liave 

 " a cafe made alfo of copper, fo much larger in diameter 

 " as to admit a thin (heet of water to circulate between 



K k 2 *' them 



