354 
Proceedings of Royal Society of Edinburgh. 
Calcareous Structure — consisting of — 
Total. 
Chitin. 
Carbonate 
of Lime. 
Phosphate 
of Lime. 
Percentage. 
Carapace, .... 
Chelae, 
Ambulatory limbs, 
Abdominal segments, . 
817 
1184 
736 
156 
63 
150-32 
236-80 
147-20 
31-20 
12-60 
656-80 
933-00 
579-97 
122-93 
49-64 
9-87 
14-20 
8-83 
1-87 
•76 
Outer. 
Chitin, . 20-00 
CaO,C0 2 . 78-80 
3Ca0,P0 5 . 1-20 
100-00 
Inner. 
Chitin, . 34-00 
CaO,C0 2 . 65-00 
3Ca0,P0 5 . 1-00 
Outer structure weight, 
2956 
578-12 
2342-34 
35-53 
Inner structure, . 
103 
35-00 
66-98 
1-02 
Teeth (mandibles) weighed, . . 17 grains. 
Stomachical teeth (horny matter), . 27 ,, 
100-00 
TABLE V. — Lymph from Edible Crabs. 
When in condition, one of these crabs, weighing about 8000 grains, 
gave from its lymph — 
Phosphate of lime, . . . 11 ’10 grains. 
Phosphoric acid (P0 5 ), . . 15 *78 ,, 
The latter probably present in combination with albumen or as alkaline 
phosphates. 
Another crab, about same weight, but out of condition, gave — 
Phosphate of lime, . . .0 '898 grains. 
Phosphoric acid (P0 5 ), . . 4 '967 ,, 
Theoretical Description of a New “Azimuth Diagram.” 
By Capt. Patrick Weir. Communicated by Sir Wm. 
Thomson. 
(Read July 15, 1889.) 
About thirteen years ago, when officer of a vessel trading from 
London to Australia, and in the daily practice of verifying the 
error of the compass by azimuth’s declination, the idea first occurred 
to me of projecting the sun’s path on the plane of the horizon; and 
during the voyage I succeeded in solving the problem, and con- 
structed a diagram which I used daily while at sea for several 
years, until I gave up long voyages, and had no further occasion to 
trouble about azimuths. 
