tcylla and Charyhdis.— Refining of Nitre, 25* 



ffte fides of Africa met and cialhed together; where contending winds, whofe power was 

 greater in the boundlefs ocean ; where mountainous waves, rocks, and whirlpools threat- 

 ened inevitable deftruftion ! What preparations, what caution were thought neceflary for 

 the {hip whicli was to make this dangerous paflage ? Able pilots who had frequently mada 

 the voyage ; marts and yards fecured by additional ropes ; a large fupply of falls and cables,, 

 thicker and ftronger than ufual ; and a double rudder, that in cafe one fhould be damaged; 

 tliere might be another to aft. The mariners wer« to be fadened to their pofts by ftrong 

 ropes ; the paffengers (hut down below, and the deck left clear for the crew ; a number of 

 whom ftood with hatchets in their hands, ready to cut away the mafts fliould it be neceflary. 

 The guns were flowed in the hold as ballaft, and the port-holes, windows, and every kind' 

 of aperture, carefully clofed. Such were the precautions taken in the laft century, on' 

 doubling the Cape of Good Hope ; but how few of them are now neceflary to perform this 

 voyage in perfedl fafety ! Of this I have had the fatisfaftion to be certified by an- 

 Englifh gentleman, Mr. Macpherfon, with whom I had the pleafure of converfihg in 

 Pavia, in July 179:0; and who had twice doubled this Cape in his voyages to India ; a-. 

 gentleman of great refpe£i:ability for his information, for the various long voyages he has 

 made, and the honourable employments he has held. 



The facility with which this paflage may now be made, is therefore the confequence bf 

 the perfedion to which the art of navigation has arrived; and the fame we may conclude 

 with refpe£l to Charybdis and Scylla, whicli at prefent have nothing terrible but the name, , 

 to thofe who pafs them with the requifite precautions. 



V. 



hflruBions for refining Saltpetre by a new Procefs. By J. A. CSAPTALy J. P. ChaMPT and: 



Bon JOUR *. 



X HE crude faltpetre is to be beaten fmall with mallets, in order that the water may more 

 eaGly attack every part of the mafs. The faltpetre is then to be put into tubs, five or fix- 

 ' hundred pounds in each tub. Twenty per cent, of water is to be poured into each 

 tub, and the mixture well ftirred. It muft be left t& macerate, or digeft, until the fpecific. 

 gravity of the fluid ceafes to augment. Six or feven hours are fufficient for this firft ope-- 

 sation, and the water acquires the denfity of between 25 and 35 degrees. (Sp. Gr. 1.21, 

 and 1.306. See Philof. Journal I. 39.) 



The firfl; water muft then be poured ofi^, and a fecond portion of water muft be poured 

 on the fame faltpetre amounting to 10 per cent. ; after which the mixture muft be ftirred 

 up, fuffered to macerate for one hour, and the fluid drawn or poured ofi^. 



Five per cenj, of water muft then be poured on the faltpetre ; and after ftirring the whole, 

 the fluid muft be Immediately drawn off. 



When the water is drained from the faltpetre, the fait muft be thrown into a boiler con- 

 taining 50 percent, of boiling water. When the folution is made, it will mark between 66 

 and 68 degrees of the hydrometer. (Sp. Gr. 1.848, and 1.898.) 



* Tranflated from the Journal de Phyfique, bearing date Auguft 1794) but lately publilhed. 



The 



