338 General Notes. % [ May, 
taken by.a committee or by any society or group of societies, 
should be suggestive or advisory and not positive or dig orial. 
here may even be some who believe that_nothing uSeful can 
be accomplished in this field; but a second ught may show 
that much good can be effected, without doin ything of doubt- 
ful expediency. It seems unfortunate that in the suggestions of 
the congress more prominence was given to those points in re- 
gard to which there is greatest difference of opinion, and most 
intelligent doubt as to what ought to be done, than to the more 
important want underlying them. What we need is precision, 
first, and afterwards uniformity of nomenclature if we can get it. 
The essential part, on which all should agree, is that statements 
of size and distance should have a definite meaning; that when 
an author mentions, for instance, the 1—1000 of an inch, or the 
I-100 of a centimetre or of a millimetre, that statement should 
mean one and the same thing to him, the writer, and to all intel- 
ligent readers. This certainly is not true in regard to the mea- 
surements made and recorded with the microscope in the past or 
at the present time. The best stage micrometers in use, as a 
basis for measurements, are well known to differ among them- 
selves by various and easily measurable discrepancies which must 
represent errors on one side or both. In comparing micrometers 
from different sources, differences of two per cent. have been often 
noticed, and sometimes as high as six per cent. Far less errors 
than these, and as are quite generally present, must greatly im- 
pair the scientific value of all measurements; and it may be safely 
said that the exact degree of accuracy of the instruments used, 
and therefore of the measurements recorded, by observers with 
the microscope, is seldom known to the authors themselves, and 
scarcely ever to the readers of their papers. Nor can individual 
care and labor overcome this difficulty. A student can reject 
1-3600th of the standard yard in London or of our national copy 
of that standard in Washington, is a most valuable result which 
can be attained only by concerted action, and is well worthy the 
labor of any committee or of any society. We need a tangible 
inch, whether called a “standard” or not, which should be, as 
nearly as can be detected by the modern ee or by any 
other known means, the 1-36th part of the sta yard; ora 
centimetre corresponding equally well with the 1-10o0th of the 
standard metre; or some other equally determined unit, which 
should be officially recognized as authority for all who desire the 
greatest attainable accuracy. If so accurate a subdivision exists 
ong the national standards at Washington, it might be verified 
_by the committee, and arrangements sought from those having it- 
