On a Species of Plumbago from Africa, 41 



Jteference to the Engravings and Section of Mr. Waist Ett's 



Improvement of the Dibble for planting Acorns. Plate 



II. Fig. 2, 3, and 4. 



a represents the handle of the dibble, which dibble is a 

 rod I of au inch in diameter, moveable in the tube of a 

 stave, which stave is externally about two inches diameter. 

 f} a tin or metal tube fixed on the exterior part of the stave, 

 and of the same bore or aperture of the tube of the stave : 

 when a hole is made in the earth by the point of the dibble 

 d, the acorn is dropped down the metal tube, and on 

 drawing up the dibble by its handle to the height of the 

 letter e, the acorn c passes through a large opening into 

 the dibble tube, and from thence falls into the hole made 

 ■^ " by the point of the dibble in the earth, when bv moving 

 , backwards and forwards the cross handles g g, fixed on the 

 ■••top of the hollow stave, the soil surroundmg the hole in 

 the earth is loosened by the iron wings yy and deposited 

 on the acorn. Fig. 4, h shows a section of the iron wings 

 ff belonging to the bottom of the hollow stave. 



Supposing that you wish to plant an acorn in the middle 

 of any bush, you are to press the instrument through it 

 into the ground, make a hole in the earth by the point of 

 the dibble rod, then raise the rod above the hole where 

 the two tubes communicate, drop the acorn down the tube 

 /', which falls immedialelv through it and the lower part 

 of the stave-lube into the hoie previously made by the rod, 

 which hole is instantly covered by the soil raised by the 

 wings. The dibble rod may be occasionally passed down 

 the metal tube, to be certain of its being perfectly clear. 



IX. Examination of a Species of Plumbago from Africa. 

 By Edmund Davy, Esq. Chemical Operator and Su- 

 perinlcndunt of the Mineralogical Collection in the Royal 

 Institution. Communicated by the Author. 



JL HIS substance was brought from Mr)zambique, on the 

 conlinenl <^i' Ai'rica, where it is said to occupy a consider- 

 able extent of surface. I am not aware that it has been 

 d.'sciibed by mineralogical writers ; I shall therefore notice 

 its physical and chemical properties. 



Its colour is iron-gray. It is disseminated in small la- 

 minae, in a loosely aggregated matriv, composed of feldspar, 

 quartz, and mica. 'I'he laminae intersect each other in 

 different directions, but exhibit no apjiearance of crvstalliza- 

 tion. hs lustre is metallic, like that of polished steel. It 



is 



