380 Chronicles of Science. i[July, 
appreciated when they are weak than when both are strong. He 
finds that, as Mr. Huggins had anticipated, the spectrum of hydrogen 
may be made, by sufficiently diminishing the light, to present the 
middle line only, which is that visible in the nebula. 
Mr. Stone supplies a valuable paper on the rejection of dis- 
cordant observations. His theory is that the rejection of such 
observations cannot be made except upon a direct admission of 
carelessness on the part of the observer; and he shows how the 
amount of error which justifies a rejection is to be calculated from 
an estimate of the average number of mistakes made by the observer 
in a given number of observations. 
Mr. Chambers supplies a catalogue of binary stars formed (in 
the main) by reducing to the year 1870 the stars in the excellent 
catalogue presented by Mr. A. Brothers, to the Manchester Literary 
and Philosophical Society. 
Mr. Proctor puts forward a proposal for a new star-atlas. The 
advantages of the plan appear to be the following :—The stars 
would be presented in a moderate number (12) of maps, uniform 
in size, shape, and mode of projection; with scarcely appreciable 
distortion and scale-variation; not too large for convenient use 
(about 12 inches in diameter), and yet on the sufficiently large scale 
of an 18-inch globe. The twelve maps would correspond to the 
twelve pentagonal maps of his gnomonic set, but being made circular 
and thus overlapping, the connection between the different maps 
would be conveniently exhibited. 
We must leave to our next number the review of several inter- 
esting papers which appear in the latest number of the Society’s 
Proceedings. The issue of this number having been delayed for the 
completion of a lithograph, illustrating Mr. Abbott’s paper on 
certain variations in the nebula surrounding 4 Argts, we have 
received the number too late for discussion here. But we are glad 
to notice that there now occurs less delay than took place some few 
months ago in the issue of the Society’s notices. 
4. BOTANY AND VEGETABLE PHYSIOLOGY. 
Green Rotten Wood.—We have received the following from Mr. 
H. C. Sorby, F.R.S.:—*In the last number of your Journal 
(p. 222) you call attention to the colour of green rotten wood, and 
ask whether it has any relation to the Phycocyan of Cohn. I have 
examined it carefully, and find it is quite distinct from that or any 
other colouring matter with which I am acquainted. The chief con- 
stituent is a green-blue colour, insoluble in water and only sparingly 
soluble in alcohol or benzole, and not fluorescent ; whereas Phyco- 
cyan is soluble in water and very fluorescent. The spectra are 
