X INTRODUCTION. 



how to tran fport them with effect to any part where they 

 appear to be wanting. 



Anot her greater and ineftimable advantage is, that all land- 

 fcapes, and views of the country, which conftitute the back- 

 ground of the picture, are real, and in the reality fhew, very 

 ftrikingly indeed, in fuch a country as Africa, abounding in 

 picturefque fcenes, how much nature is fuperior to the crea- 

 tion of the warmeft genius or imagination. Momentary 

 mafTes of clouds, efpecially the heavier ones, of flormy Ikies, 

 will be fixed by two or three unftudied flrokes of a pencil ; 

 and figures and dreis, in the moll agreeable attitudes and 

 folds, leave traces that a very ordinary hand might fpeedily 

 make his own/or, what is Hill better, enable him with thefe 

 elements to ufe the afliftance of the bell artift he can find in 

 every line of painting, and, by the help of thefe, give to 

 each the utmoft poflible perfection ; a practice which I 

 have constantly preferred and followed with fuccefs. 



It is true, this inftrument has a fundamental defect in 

 the laws of optics ; but this is obvious, and known una- 

 voidably to exift ; and he muft be a very ordinary genius 

 indeed, and very lame, both in theory and practice, that can- 

 not apply the necefTary correction, with little trouble, and 

 in a very fhort time. 



I was fo well pleafed with the flrft trial of this inftrument 

 at Julia Caifarea, now Sherfhell, about 60 miles from Al- 

 giers, that I commifTioned a fmaller one from Italy, which* 

 though negligently and ignorantly made, did me this good 

 fervice, that it enabled me to fave my larger and more 



perfect 



