438 
or Chemung near Oneonta, and that, according to 
assays, the rock will yield per ton from fifty to a hun- 
dred and ninety-five dollars of gold and silver. In 
this paper the result of a series of assays was given, 
and no one indicated more than three dollars of silver 
to the ton of ore. There is in some of the rocka 
‘small amount of galena; and in this, from one to 
two ounces of silver in a ton of ore, but not any gold. 
Society of arts, Massachusetts institute of technology. 
-May 8. — Prof. Edward C. Pickering addressed the 
society on the proper method of measuring colors. 
After referring to the difficulty of measuring color 
and in obtaining a proper unit for measurement, the 
speaker referred to the ordinary phenomena of color, 
and the effect of various bodies on the rays of light; 
dwelling, among other things, upon the effect of a 
large index of refraction in increasing the brilliancy 
of a body. The explanation was suggested, that the 
increased brilliancy of the so-called straw diamonds, 
so lately the subject of comment, and which were 
said to have been made of glass and painted, might 
have been due to a deposit upon them of a very thin 
layer of silver. The speaker said that the subject of 
color had generally been studied subjectively, that is, 
by its effect on the eye, and not objectively, as a phe- 
nomenon in itself. The generally accepted theory 
of color was explained, by which it is supposed that 
the eye can distinguish three primary colors, — red, 
green, and a bluish violet; and the objections to the 
use of Chevreul’s color-circle as a means of measur- 
ing and distinguishing color were referred to. By 
the objective method of studying color, we may de- 
termine the intensity of each portion of the spectrum 
by a thermopile or bolometer, or by photography, or, 
again, by means of the instrument proposed by Vie- 
rordt, by which the lower half of the slit of a spectro- 
scope can be varied in width until any part of the 
corresponding spectrum shall be just equal in bright- 
ness to that coming from the upper half of the slit, 
through which is passed the light to be measured. 
The amount of opening of the lower half of the slit 
affords an invariable scale for the measurement of 
the relative intensity of two lights. Professor Pick- 
ering had experienced numerous difficulties in experi- 
menting with Vierordt’s instrument, especially when 
the lights differed greatly in intensity. The photo- 
spectroscope which he had finally perfected was ex- 
hibited and described. It consists of a spectroscope 
with two slits, in which the relative intensities of two 
spectra may be measured by polarized light. Special 
devices were employed to render the images to be 
compared well defined on their edges, and of uni- 
form brightness. The instrument allows of many 
practical applications in the measurement, by abso- 
lute standards, of paints, dyes, inks, glass, and the 
comparison of lights from various sources. Another 
application is to the measurement of the colors of 
stars, the chief difficulty being lack of light. In this 
measurement, Professor Pickering had modified the 
method of Professor Pritchard, who had compared 
the light of different stars by extinguishing them 
with a wedge of shade-glass, measuring by a scale 
SCIENCE. 
[Vou. III., No. 71. 
the point at which they ceased to be visible. Pro- 
fessor Pickering had measured the relative intensities 
of the different colors by spreading out the light of 
the star into a spectrum, and allowing the star to 
transit along the wedge, the time of disappearance 
of each color being noted. The exact color is deter- 
mined by a series of slits. All the spectra are 
brought into the same position by an auxiliary image 
brought into the field by means of a plate of plain 
glass cemented to the side of the principal prism. 
The results given by this instrument are very en- 
couraging, and promise to give a satisfactory meas- 
ure of the intensity of each part of the spectrum of 
the stars, 
Biological society, Washington. 
May 3.—Dr. R. W. Shufeldt remarked in the 
course of his description of a pair of ribs on the oc- 
cipital bone of the large-mouthed black bass, Microp- 
terus salmoides, that recently he had made anumber 
of dissections of this fish, and. in every instance had 
found a pair of ribs upon the occipital bone, just 
above and internal to the foramen of the vagus nerve 
(see Science, Nos. 65 and 69). They are without epi- 
pleural appendages, but otherwise like the abdomi- 
nal ribs. If this fact be new to science, it is a very 
interesting discovery, of great morphological sjgnifi- 
cance, and introduces an important factor in the theo- 
ry of the segmentation of the skull. It had not been 
noticed in any of. the prominent works upon compar- 
ative anatomy generally used as text-books, nor in a 
recent and very thorough article by Dr. Sagemeh! up- 
on the cranial osteology of Amia caloa (Morph. jahrb., 
1883). Dr. Shufeldt had also discovered these ribs 
thoroughly developed in the tunny, Orcynus thynnus, 
and thought that they would doubtless be found in 
others of the Scombridae and Centrarchidae. 
Dr. T. Gill briefly reviewed the salient structural 
features of the various representatives of the order 
Squali, as well as the history of the classification of 
the group, and claimed that there were five principal 
types of structure manifested in the various forms, 
whose anatomy is more or less satisfactorily known: 
1°, the Pternodonta, or Selachophichthyoidi, repre- 
sented by but one known species, lately described by 
Mr. Garman (Science, No. 52); 2°, the Opisthar- 
thri, of which the Notidanidae or Hexarchidae are 
the only known forms; 3°, the Proarthri, of which 
the Heterodontidae, represented by the well-known 
‘Port Jackson shark,’ forms the only existing family; 
4°, the Anarthri, to which belong all living sharks 
excepting those now specifically eliminated; and, 5°, 
the Rhinae, to which belong the family Squatinidae, 
including the so-called ‘angel-sharks.’ ‘The speak- 
er was inclined to consider several of these more 
than sub-ordinal, and rather as of ordinal value; 
but, until they had been better studied, he would 
reserve opinion on this question. ‘There was one 
type, represented by the extinct Cladodontidae, whose 
position was doubtful. For these he had formed the 
group Lypospordyli; but it was not evident whether 
it belongs with the true Squali, or whether it may’ 
not be related to the Holocephalus, the character of 
the branchial arches being dubious. ——- Mr. N. P. 
