On ihs Geog'nosy of Madeira , $c. 
“ A Funchal la temperature des caves paraite £tre, de 16® 9t C. 
(61° F.), par consequent de 4° 6' (71° 9' F.) au dessous de la 
temperature de Pair. Nous reviendrons dans la suite sur cette 
difference remarquable entre les souterrains a l’isle de Madere 
et 1’atmosphere circonvoisine I think I may venture to con- 
tradict this anomalous difference. There is not a subterraneous 
cellar or crypt in the island : the deepest caverns are the “ Fur- 
naces of St John/'’ (close to Funchal on the NW., and about 
240 feet above the sea), formed out of a deep bed of scoriae. 
In the largest (128 feet to the innermost part, which is wide, 
spacious, and lofty, and about 15 feet below the level of the 
mouth), I made the following observations. Nov. 4., 1 p. m.. 
Temp, of air 71° 5, Hyg. 51°, Temp, of the inmost part of the ca- 
vern 67°, Hyg. 73^°. Jan. 4., 2 p. m.. Temp, of air 66°, just with- 
in the month 64°, inmost part 63^°. Again, in the cavern at 
Phaye Formosa, close to the sea, about three miles west of Fun- 
chal, and upwards of 39 feet deep, I found a difference of on- 
ly 3° F. ; and in that of St Roque, about 1000 feet above the 
sea, north of F unchal, and nearly 60 feet deep, a difference of 
only 4° F. There is an extraordinary difference, however, be- 
tween the temperature of the wells and that of the air of Fun- 
chal, the former (Mr Lundie’s, Mr Young’s, and Mr Sortie’s, 
all upwards of 20 feet deep, and in the open air,) being 58°, 
when the latter was 69° ; but this is explained by recollecting, 
that these wells are supplied by streams which descend from 
heights of 3800 feet behind the town, where there would be a 
corresponding difference in the mean temperature ; for that of 
the spring near the Mount Church, (inclosed at the expence of 
Consul Murray), and about 1900 feet above the wells in ques- 
tion, was 58°, the air within being 62°, by an observation which 
I made in October. 
Art. XX.* — Account of Mr Ronalds' Pendulum Doubler ofEleo * 
tricity . 
In a work just published by Mr Ronalds, entitled, “ Descrip. 
tion of an Electrical Telegraph, and of some other Electrical 
* Humboldt. Annales de Chimie , p. 602. lie!. Hist., p. 424. 4to. I quote 
my MS* extracts from these expensive works, and have omitted to note the vo- 
lume. 
