418 APPENDIX. 
whether he measured from the top of a head of coral, or from the solid bank 
on which the corals were growing: and, further, that the use of our “ excel- 
lent spirit level” from a stone of so little length is not sufficiently exact for 
correct results, and hence they draw no conclusions from their trials. 
Before leaving the region, they made the following arrangements with 
reference to future measurements. They planted two blocks of coral, cement- 
ing them below, nearly burying them in the soil, placing them 0.21 metres 
above the Wilkes’ stone, which is between them. ‘They then put a mark 
upon them on plates of metal directed toward the place of observation on the 
shoal. A third stone was placed forty metres from the southwest angle of 
the Point Venus lighthouse, in order to give a second observation on the 
position of the spot on which the soundings were to be made. This spot was 
found to bear from the two new stones N. 77° 30’ E.; from the third stone, 
N. 70° 55’ E ; from the bell of the new Mission Church, S. 81° 40! E. A 
horizontal line passing from the mark on the new stone is 7.460 metres above 
the madreporic heads. 
They also made observations which satisfied them that Tahiti was not at 
present undergoing any general elevation. ‘Two maps accompany the pam- 
phlet: one is copied from Wilkes; the other is from a chart by Lieutenants 
Le Clere and Minier, and contains lines showing the positions of the points 
referred to above. See page 246. 
The following letter on the Rate of Growth of Florida Corals, for which 
the author is indebted to Mr. H. T. Woodman, the investigator of the subject, 
was received too late for the use of the facts in the earlier part of this work. 
It is dated :— 
BurrFato, N. Y. Jan. 25, 1890. 
** Herein I enclose a copy from the diary which I kept while on the Florida 
Reef during the winter of 1881-82. It gives almost the exact growth of such 
massive corals as I found or placed in a shallow channel across the reef just 
east of the Tortugas Group in the winter of 1867-68. The water on the reef 
at this point was only about three feet deep with two feet more in the chan- 
nel at lowest tide. From the healthy appearance of the Madrepora cervi- 
cornis on both sides of the channel, with Miilepora alcicornis and Porites 
clavaria in close proximity, as well as good specimens of Meandrina labyrin- 
thica, Orbicella cavernosa, and a Dichoccenia within a few feet of the centre 
of the channel, I was inclined to think that no more favorable locality to 
watch the growth of some of the massive corals could be found. I therefore 
added to the above-named massive forms, a Siderastrea, Orbicella annularis, 
Porites astreoides, Diploria cerebriformis, Manicina areolata, Meandrina 
sinuosa, and M. clivosa. 


