470 Cambridge Philosophical Society :— 
‘picture. He showed, by a collection of examples from the best 
English poets, that the established meanings of the word ‘“argu- 
ment’”’ are reducible to three: (1) a proof or means of proving; 
(2) a process of reasoning or controversy made up of such proofs; 
(3) the subject matter of any discourse, writing, or picture. And he 
maintained that the second of these meanings ought to be excluded 
from scientific language. 
December 12.—The following paper from the Astronomer Royal 
was read, ‘‘Supplement to the proof of the Theorem that ‘ Every 
Algebraic Equation has a Root.’ ” 
‘he author expressed his want of confidence in every result ob- 
tained by the use of imaginary symbols, and in this supplement 
demonstrated that the left-hand member of every algebraic equation 
of the form ¢(#)=0 admitted of resolution, either into real linear 
factors, or into real quadratic factors. 
Professor Miller also made a communication ‘‘ On a new portable 
form of Heliotrope, and on the employment of Camera Lucida prisms 
and right-angled prisms in surveying.” 
February 13, 1860.—The Rev. H. A. J. Munro read a paper . 
“On the Metre of an Inscription copied by Mr. Blakesley, and 
printed by him in his ‘ Four Months in Algeria,’ p. 285.” 
February 27.—The Rev. Professor Sedgwick made the following 
communications :— 
1. ‘* Anaccount of Mr. Barrett’s progress in the Survey of Jamaica, 
with some remarks on the Distribution of Gold Veins.” 
2. ‘“Some account of the Geological Discoveries in the Arctic 
Regions.” 
March 12.—The Rev. Professor Challis made a communication 
‘On the Planet within the orbit of Mercury, discovered by M. 
Lescarbault.” 
By a recent comparison of the theory of Mercury’s orbit with 
observation, M. Leverrier found that the calculated secular motion 
of the perihelion of that planet requires to be increased by 38", and 
that this difference between observation and theory cannot be ac- 
counted for by the attractions of known bodies of the solar system. 
In a letter addressed to M. Faye, and published in the Paris Meteo- 
rological Bulletins of October 4, 5, and 6, 1859, he suggested that 
the difference might be due to the attraction of a group of small 
planets circulating between Mercury and the Sun. On December 22 
of the same year, M. Lescarbault, a physician and amateur astro- 
nomer, residing at Orgéres, about sixty miles south-west of Paris, 
announced in a letter to M. Leverrier that he had seen on March 26, 
1859, a small round spot traversing the sun’s disc, which he con- 
sidered to be a planet inferior to Mercury. Naturally much inter- 
ested by this information, M. Leverrier went to Orgéres on Decem- 
ber 31, and after closely interrogating M. Lescarbault respecting the 
particulars. of the observation, and the instrumental means by which 
