VOL. XXIV.] PHILOSOPHICAL TRANSACTIONS. l6l 



part, with sqrpa, lay inwards, as is represented by h in fig. 1] ; and in fig. 10 

 lay on the outside of the leaf, as is shown by bc. Now these parts, which in 

 fig. 10 are cut across between ab and cs, are the very same parts which in 

 fig. 6, iKLM, are represented lengthwise, with this difference only, that fig. 10 

 is drawn from a less microscope. 



Having squeezed the sap out of the aloes-leaf, in order to discover what salt 

 particles would coagulate in the same ; I placed it on my escritoire, and always 

 observed, that when the water was mostly evaporated, there remained abund- 

 ance of salt particles behind, which were almost all of them quadrangular figures, 

 and of a cubical thickness, as is represented at ik, fig. 13 ; and again some 

 smaller at lm, fig. 14 ; and others much smaller, as in fig. 15, l6 ; nay, some 

 of them were so exceedingly small, that they almost escaped the sight, even 

 through the microscope; insomuch that one i^ould not judge whether those 

 salts were round or square. 



I observed also some figures of salt that were composed of several coagulate;d- 

 after such a manner, that their shape could not be described; and among others, 

 there was one salt particle that was composed of four others, joined together 

 cubically, as represented at no, fig. 17- t saw another salt likewise, that was 

 made up of 20 quadrilateral salt particles coagulated together, viz. 5 in length 

 and 4 in breadth; and another salt, in which 1 counted 30 particles joined after 

 the same manner. When I took the sap out of an aloes-leaf, whose vessels 

 contained a yellow sap, I saw the salt particles lying so clear, as if they were 

 little pieces of glass ; and as they were surrounded with a fine peach colour, it 

 was a very agreeable sight. 



From my observations on the salts, I was led to consider the aloes itself, as 

 it is used in the apothecary's shops. Having taken a piece of aloes, and beaten 

 it small, I wrapped it up in a paper, and put it into a clean glass, pouring rain- 

 water upon it, in which I let it infuse 2 or 3 days ; then pouring off the top of 

 it, I caused it to evaporate, and then discovered a great number of salt particles, 

 of the same shape and proportion as those represented in fig. 14, 15, l6, and 

 17. There were also coagulated a great many salt particles, of the figure re- 

 presented at EFGH, fig. 5, only with this difference, that they were something 

 shorter and thicker in the middle, and some of them not so even or smooth as 

 in the said figure. 



I had sent me also a small plant of dragon's blood ; in which I viewed the 

 stalk of the leaf after I had cut it across, and discovered at the same time several 

 particular colours of a light and of a deeper red ; and I observed in the said 

 stalk little places in which I could perceive no colour ; but on cutting the same 

 stalk lengthwise, I could then see that those places were canals, through which 



VOL. V. Y 



