May 25, 1372.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
049 
of both plants correspond with the Ipecacuan root of 
English commerce. 
The native tribes of Brazil have long known the effi¬ 
cacy of the Ipecacuan root in the treatment of disease. 
The native names for it are Poaya do Mato and Cipo. 
In the Minas-Gcraes it is called Ipecacuanha. The 
Ipecacuan plant appears to have been first noticed by 
Samuel Purchas in ‘His Pilgrimes.’ In this work he 
gives an account of voyages made to South America. 
He states that his treatise on Brazil (part iv. book vii. 
p. 1311) was written “by a Portugal friar (a Jesuit), 
who had lived for thirty years in those parts, from whom 
(much against his will) the written book was taken by 
Mr. Francis Cooke, of Dartmouth, on a voyage out¬ 
ward bound for Brazil, anno 1601, who sold the same to 
Master Ilacket for twenty shillings, by whose permission 
it was translated out of Portugal into English.’’ Mr. 
'• R- Markham mentions that this treatise was signed 
Mansel Tristan, Enfermero de Collegio de Baya. In it 
there is an account of a plant called Igpecaya, or Pigaya, 
which is said to be profitable for the bloody flux, and is 
supposed to be Ipecacuan. 
In 1648 it was described and figured by Piso and 
Marcgrav in their treatises on the natural history of 
Brazil, which were published together, viz., Piso, * De 
Medicina Brasiliensi,’ p. 101, Marcgrav, ‘ Historia 
Rerum Naturalium Brasil eg,” p. 17* It was then intro¬ 
duced into Europe. Grenier, a merchant, brought it to 
Paris as a pharmaceutical remedy, and as such it was 
used by Jean Adrien Helvetius, a medical man. It was 
brought under the notice of Louis XIV. Experiments 
were made at the Hotel Dieu as to its efficacy in diar¬ 
rhoea and dysentery. The origin of the name is doubtful. 
Some say Ipe (bark), caa (plant), cua, (scented), nha 
(striped), that is, bark of a scented and striped plant. 
Martins, in his ‘ Specimen Materise Medicos Brasiliensis,’ 
states that the name is corrupted into Picahonha, and 
by the Brazilians into Poaya. The latter name is ap¬ 
plied generally in Brazil to all kinds of Ipecacuan 
plants. Weddell says that it is a corruption of the 
Indian words, Ycipo ayaca, which mean a twining 
(cipo), assuming a basket form (liane a panier, a basket 
twiner). 
^ From Weddell’s account in the ‘Annales des Sciences 
Naturclles, Botanique,’ tom. xi. (1849), 3 series, p. 193 
et seq., we gather the following particulars :— 
Ipecacuan is found in parts of Brazil, bordering on 
the Atlantic, Para, Maranhao, Pernambuco, Bahia, Spiri- 
to-Santo, Minas-Geraes, Rio Janeiro, and San-Paulo. 
The plant also extends to Bolivia ; it was seen by Wed¬ 
dell in Matto Grosso, a large Brazilian province far in¬ 
land. 1 le found it in shady parts of the province among 
such plants as Euterpe oleracea , (Enocarpus Bacaba, Cocos 
capitata , species of Mauritia , Tree-ferns, and Iriartea 
exorrhiza. 
(To be continued.) 
THE IDENTITY OF LIGHT AND RADIANT 
HEAT. 
BY rnOFESSOR TYNDALL, LL.D., F.R.S. 
Whether we regard its achievements in the past, or 
its promise and tendency in the future, all that we know 
of physical science—every bent and bias which we 
receive from its pursuit—tends to confirm the dictum of 
the poet regarding this universe :— 
“ All are but parts of one stupendous whole, 
Whose body Nature is.” * 
If I halt here, and omit the next clause of the couplet, 
it is not because physical science has arrived at any con¬ 
clusion hostile to that clause, at all events in its pro- 
foundest signification, but simply because what the poet 
* “All are but parts of one stupendous whole, 
W hose body Nature is, and God the soul.” 
Pope’s ‘Essay on Man,’ Epistle I. line 2C7. j 
goes on to affirm lies outside the sphere of science. We, 
as physical students, have to do with “Nature” only, 
and our view of nature could not be more happily ex¬ 
pressed than by the figure employed by the poet. For 
our vocation, and the delight and discipline that it con¬ 
fers, do not consist in the registration of unrelated facts 
and phenomena ; but in the searching out and discovery 
of relationship in a system, whose parts we hold to be 
as closely and definitely related to each other as are the 
various organs and functions of the living body itself. 
It was this spirit of search, this capacity and desire, 
developed amid natural agencies, to detect the lines of 
connection between these agencies, that gave for a time 
such keen interest to the discussion, whether light and 
beat were essentially different things, or whether a sub¬ 
stantial identity subsisted between them. It is not so 
very many years since that most excellent experimenter 
and philosophical inquirer, Melloni, isolated from a solar 
beam a brilliant light, and finding it incompetent to 
affect his most sensitive thermoscopic apparatus, con¬ 
cluded that light and heat were essentially distinct. 
But in drawing this conclusion, Melloni forgot that he 
was implicitly dealing with an instrument of almost in¬ 
finitely greater delicacy than his thermoscopic apparatus; 
he forgot that the human eye, and the consciousness 
connected with the eye, are capable of being vividly ex¬ 
cited by an amount of force which when translated into 
heat might defy all the thermometers in the world to 
detect it. Melloni himself subsequently modified his 
conclusion. 
It is not so very long since the late Principal Forbes 
was eagerly engaged in establishing the important point 
that radiant heat, like light, is capable of being polarized. 
Since that time Knoblauch, Foucault, Fizeau, and See- 
beck have applied their refined experimental skill to this 
question of identity; and those excellent investigators 
De la Provostaye and Desains, pushed the analogy 
between light and heat so far as to prove that the mag¬ 
netization of a ray of light, in Faraday’s sense of the 
term, has its parallel in the magnetization of a ray of 
heat. 
It was, however, in their private cabinets that these 
experimenters obtained their results, which were in most 
cases so small, as to require attention on the part of a 
skilled observer to detect them. But science grows, and 
our experimental means augment as our knowledge 
expands. Recent discoveries and improvements will, I 
trust, enable me to make evident to y r ou, to-night, effects 
which have been hitherto confined to far more limited 
circles; some of which indeed have only been seen by 
the observers who first noticed and described them. 
And if those accidents which often hold sway over lecture- 
experiments of a delicate character should prove favour¬ 
able, we may be able to push the subject a hair’s breadth 
beyond the limits which observation has hitherto as¬ 
signed to it. 
Heat is presented to us in two aspects: sometimes 
associated with ordinary matter, through which it creeps 
1 by the process of conduction ; sometimes not associated 
with ordinary matter, but, like light, flying through 
space with immense velocity. In this latter form it is 
: called radiant heat. Radiant heat obviously and palpably 
comes to us from the Sun, but here it is entangled with 
j light. Let me, in the first place, endeavour to unravel 
I this entanglement. 
I When white light is refracted, it is unravelled and 
the spectrum is produced. A spectrum of the electric 
light was thrown upon a screen ; and red, green,. and 
black ribbons about an inch wide were successively 
■ moved along it. The red placed in the red light ap- 
' peared a brilliant red; when moved into the green it 
J became black. In like manner, the green ribbon moved 
! from the green, where it shone vividly green, into the 
red, became an intense black. The black ribbon was 
I black in every part of the spectrum. 
Now the red ribbon is not heated in red, and tho 
