chiefly Chemical. 261 



rind, collocted eliiefly in the pulp enveloping ttie seeds. These 

 means of preservation, wq too well know from experience, 

 have not an unlimited power. After a while they all, when 

 exposed to the influences of the elements, yield and undergo 

 change ; designed, no doubt, to promote the end for which 

 they are intended — the multiplication of their kind. The 

 tamarind is not an ex<}eption. After many weeks exposure, I 

 found the pulp enveloping its seeds dry and in part mildewed, 

 and the acid-extract covered with thick mildew. 



8. When Indian corn (maize) is exposed to the fire, it is 

 easily charred, but it is reduced to ash^s with extreme diffi- 

 eulty ; indeed, it may be said that the charcoal of this grain 

 is almost incombustible. It owes this property to the large 

 proportion of phosphate of magnesia it contains in conjunc- 

 tion with a little phosphate of lime. Tfiis is proved by di- 

 gesting it with dilute nitric acid. The acid dissolves these 

 salts, and after their removal, the charcoal is incinerated 

 without difficulty. 



Owing to its property of resisting the fire, it has aecurred 

 to me, that this glazed charcoal may be advantageously em- 

 ployed as a varnish for pottery. It has iJie properties, in 

 the most essential respects, of the admired black varnish of 

 the pottery of Ancient Greece and Etruria ; and I apprehend 

 its effect would be as pleasing to the eye as a red ground, 

 and that it would be equally durable. I hope it may have a 

 trial. 



9. When Indian corn is digested with dilute nitric acid 

 for a considerable time, the saline mattei*s above mentioned 

 are extracted, — a bright yellow solution is formed. If a solu- 

 tion of ammonia be added to it, a precipitate is obtained like 

 that of phosphate of lime, consisting, as seen under the mi- 

 croscope, of granules, and without any distinct crystals, as if 

 entirely destitute of the ammonian or magnesian phosphate. 

 If this precipitate is collected and heated before the blow- 

 pipe, it fuses, shewing thereby that it is not chiefly phos- 

 phate of lime ; and, if it be redissolved in dilute nitric acid 

 and reprecipitated by ammonia, the precipitate, as seen un- 

 der the microscope, has not the character of phosphate of 

 lime, but of the double magnesian salt, appearing chiefly in 



VOL. XLI. NO. LXXXll. — OCTOBER 1816. 3 



