130 Description of a Helf-Itegisterhuf Tide-Gvaje. 



Plate IV. 

 Fig. 1. Alauna rostrata. 

 ... 2. Natural size. 

 ... 3. One of the superior antcnnre. 

 ... 4. One of the inferior antenna?. 

 ... 6. Enlarged view of the anterior part of the carapace, with one of 



the footjaws projecting from its anterior edge, 

 ... 6. One of the first pair of compound legs. 

 ... 7. One of the second pair of compound legs. 

 ... 8. One of the simple legs. 

 ... 9. One of the third pair of compound legs. 

 ... 10. Caudal styles. 



... 11. Branchiae of Cuma Edwardsii, witli one of the footjawr nttached. 

 ... 12. One of the second pair of compound legs of Cuma Auduuitiii, 



with the ovarian scale attached. 



Description of a Self-Registering Tide-Gauge, invented iy Mr 

 John Maxton, Engineer, Leith.* With a Plate. Com- 

 municated b}" the Royal Scottish Society of Arts. 



The machine represented in Plate V. was designed by me for 

 registering the amount of tidal rise at any point on the coast, 

 as at a sea-port or navigable river, or in any situation where 

 it is of impoi'tance to ascertain the whole rise of the tides for 

 a length of time. Several instruments have been invented 

 for this purpose, and some of these are now in use, it is be- 

 lieved, both in this country and in France ; but that which I 

 have invented, and am now to describe, seems more simple in 

 its construction, and promises to be, at least, as well, if not 

 better, calculated to effect the object for which it is intended, 

 than any other construction that has come under my notice. 



In figs. 1 and 2, « is a plate of \ of an inch tliiclc, with 

 dovetailed feathers b b, on its surface, between which are 

 grooves represented by the dark spaces, ^ inch in depth ; in 

 these grooves are placed moveable studs, c c, which are made 

 to slide easily along the whole length of the grooves, and be- 

 fore the machine begins to operate, the whole of them are 

 set near the centre of the plate in two lines, as shewn in the 

 upper part of fig. 1. Each groove represents the rise and fall 

 of a tide ; and there being two tides in the twenty-four hours, 

 two of these grooves are employed in registering one day's 



* Read before the Eoval Scottish Societv of Arts, 28tli Nov. 1342. 



