Proceedings of the Royal Society. 205 
foree capable of lifting between 186 and 246 grains, while the 
compound process augmented the lifting power to 326 grains. In 
another, the simple process gave a lifting power of 246, the com- 
pound of 345 grains. Moreover, the efficacy of the compound 
process is much less manifest upon long than short wires : ; and 
the softer the wire the more susceptible it becomes of this magnetic 
condition. 
The author concludes this paper with some theoretical remarks 
respecting the influence of percussion in disposing the particles 
of iron to receive and retain magnetism, which he thinks {may 
tend to explain some otherwise obscure phenomena, and which 
seem to render it probable that the process of percussion may 
be applied, in connexion with other modes of magnetising, for 
giving increased power to magnets. 
Thursday, January 29. 
Thomas Amyot, Esq. was admitted a Fellow, and the following 
paper was communicated. 
Observations on the Iguana Tuberculata, the common Guana. By the 
Rey. Lansdown Guilding, B.A., &c., communicated by Sir E. 
Home, Bart., V.P.R.S. 
The author’s chief object in this communication is to correct an 
error into which many naturalists have fallen, of describing the 
gular process of some lizards as a pouch eapable of inflation, and 
to point out a new organ on the parietal bones of the head of the 
Iguana, which he proposes to name Foramen Homeanum; it 
leads to the cavity of the brain, and is covered by a brown 
oval scale, semitransparent in the centre, but not affording 
a passage to any nerve or blood vessel. 
A paper was also read, entitled 
A finite and exact Expression for the Refraction of an Almosphere, 
nearly resembling that of the Earth. By Thomas Young, M.D., 
For. Sec. R.S. 
Having shewn that if the pressure of the atmosphere be repre- 
T2 
