391 
of Edinburgh, Session 1870-71. 
composite arrangement, while the separate circuits give marked 
parabolas. 
Low Temp. 
High Temp. 
Pt.Fe., Ag. Fe. 
Deflection for 
increment of 
10° C. 
Pt. Fe. 
Deflection for 
increment of 
10° C. 
Ag. Fe. 
Deflection for 
increment of 
10° C. 
12-3° C 
39-0° C 
28-5 
10-67 
44 
16-28 
17 
6-32 
72 
61-5 
10-30 
96-0 
16-08 
36 
603 
>> 
104 
930 
10-14 
143-5 
15-55 
51-5 
5-61 
146-5 
136-5 
10-17 
202-5 
15-08 
68-0 
5-06 
12-6 
185 
172-5 
io-o 
250-0 
14-50 
77-0 
4-46 
202-5 
190-5 
1003 
268-5 
14-13 
79-5 
4-18 
12*4 
229-5 
219-5 
10-11 
298-5 
13-74 
81-5 
3-74 
251-5 
239-0 
io-o 
318-0 
13-30 
o 
r—1 
00 
3-38 
12-5 
263-0 
250-5 
io-o 
330-0 
1316 
80-0 
3-19 
272-0 
260-0 
io-o 
337 0 
12-98 
80-0 
3-19 
I find 
great difficulty 
in obtaining wires 
of the 
more 
infusible 
metals:—and I am therefore endeavouring to make a complex 
arrangement for very high temperatures with palladium and two 
very different kinds of platinum. Wires of nickel, cohalt, molyb¬ 
denum, rhodium, or iridium, or of any one of these, would he of 
immense use to me, and I should be happy to hear from any one 
whether there is a possibility of procuring them. 
2 . On Phyllotaxis. 
I was recently led to consider this subject by Professor A. 
Dickson, who showed me some of his beautifully-mounted speci¬ 
mens, and explained to me the method he employs for the deter¬ 
mination of the divergence, and of the successive leaves of the 
fundamental spiral or spirals. He referred me to two terribly 
elaborate papers by Bravais,* and I have since met with another 
of a similar character by Naumann.f These papers certainly 
cannot be supposed to present the subject from the simplest point 
of view. I do not doubt that the results I have here arrived at are 
to be found in some form or other in their pages, which are an¬ 
nounced as completely elucidating the question ; but I have not 
sought for them, my sole object having been to put what seem to me 
the elements of the matter as simply and intelligibly as I could. 
* Annales des Sciences Naturelles, 1839. 
t Poggendorff’s Annalen, 1842. 
