VOL. XIX.] PHILOSOPHICAL TRANSACTIONS. QJ 



Others. When I pursued this inquiry, I came to think of the great lobsters 

 (although there is no similarity between them and flies in their shape) which, as 

 I am informed, are caught on rocks near the seas in Norway, and are now 

 and then brought to us for sale, their feet are also surrounded with many hairs, 

 to see how these hairs, and chiefly those on the hindermost feet were con- 

 stituted, because these feet have no claws or nippers to take hold of any thing, 

 as the other feet have, and each of them is only furnished with a small claw 

 standing exactly or straight forwards, and with many small and short hairs. 

 When I brought these hairs before the magnifying glass, I saw, with great ad- 

 miration, that many hairs were furnished with two rows of many teeth-like parts, 

 which stood in very neat order one by the other, just as if we imagine that the 

 back of a knife was on each side wrought out into a row of small teeth. Here- 

 upon I imagine, that when this lobster runs up against the rocks, his feet can- 

 not slip out, being firmed by the multiplicity of these teeth-like parts. 



Microscopical Observations and Experiments. By Mr. Stephen Gray. 



N° 221, p. 280. 



Those congruous properties, known to be in small drops of water, viz. trans- 

 parency, refraction, and sphericity, led me to conjecture that they might, if aptly 

 disposed, be not unfit for microscopes, since they have the proper requisites 

 that make the glass globules excellent ones; and accordingly experience informs 

 me, that though the latter are to be preferred, yet the water, on a necessity^ 

 may be very well used, as a succedaneum to glass microscopes, which I have 

 sometimes made trial of in the following manner. 



I take a thin piece of brass, filing it into the form ab, fig. ], pi. 3, making 

 a small hole at a, which serves for an aperture; then, holding it by the other 

 end B, I pour a few drops of water on the table, taking up a small globule 

 thereof with a pin, which I lay on the hole a; then, removing the pin, the water 

 will remain on the aperture, in form of a hemisphere, or to speak with opti- 

 cians, a plano-convex lens. But if I have a mind to make a double convex of 

 water, I thrust the pin, which must be less than the hole, through ihe hole, 

 till the water be entered therein; then by drawing the pin perpendicularly to 

 the plane of the aperture, the water remains there in form of an aqueous 

 double convex lens. Then whatever I have a mind to view I take upon a pin, 

 or a piece of glass, according to the nature of the object ; and taking up this 

 natural microscope by the end b, I move the object to and fro, till it be in its 

 focus; by which means I can see objects little less distinctly, than by glass mi- 

 croscopes, especially by candle, which I find much better than day- light. 



VOL. IV. O 



