260 
PROCEEDINGS OE THE PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
necessary. Restricting my remarks to the two depart¬ 
ments of zoology and botany (on the present occasion I 
will say nothing about the geology), it is clearly evident 
that, though a single specimen of a species is a sufficient 
voucher for the occurrence of that species in the district, 
it cannot be sufficiently illustrative of the species. 
For the proper illustration it is necessary that there be 
a series of specimens showing not only the adults of each 
sex, the various stages of growth, and the seasonal 
changes, but also, so far as it is possible, the mode of life. 
The number and character of the specimens necessary to 
show all these will vary not only according to the group, 
but even according to the species, and it is not possible to 
enter into particulars just now. But, even after we have 
obtained all the examples necessary for this purpose, we shall 
still be far short of perfect completeness. Another series of 
specimens—not necessarily, however, including all the states 
and conditions alluded to above—is desirable for illustrating 
the distribution in the area over which our researches ex¬ 
tend. Perthshire and the basin of the Tay have been 
sub-divided into thirteen districts,—not arbitrarily, but 
according to the geological nature and drainage system,— 
and to illustrate the distribution properly, specimens of each 
species from all these districts, or from as many as it occurs 
in, should be preserved in the Museum. 
Some persons may think that the object to be attained 
is not commensurate with the labour and money that must 
be expended, and that a few specimens from any one part 
of the county would be amply sufficient for the purpose. 
But if there be any that think this, let me endeavour to 
show them that their idea is a mistaken one, and that in 
the interests of science, and for several reasons, it is of 
great importance that a series of specimens from several 
parts of the area should be obtained and preserved. 
In the first place, such specimens, properly authenticated, 
are vouchers for the occurrence of the species, and, as 
such, are of value in exhibiting, in the most forcible man¬ 
ner, the distribution of the species. 
In the infancy of the study of natural history—not so 
long ago—little importance was attached to the question 
of the native country of a species, much less to its distri¬ 
bution throughout the world. Of late years naturalists 
have begun to see that much light may be thrown not only 
upon the past history of species, but upon their origin and 
relationship, by a careful study of their distribution. In 
large and metropolitan museums the distribution of regions 
and countries can be illustrated ; in smaller and provincial 
museums the distribution in counties and divisions of 
counties. 
It may be thought that if the former and greater distri¬ 
bution is shown, all the information that is necessary will 
have been obtained, but the fact is, that if the causes of 
the wider distribution are to be accurately determined, it 
is in great measure by a careful study of the distribution 
in the smaller areas; hence the importance of a county 
collection illustrating the local distribution. 
It may be argued that in illustrating the distribution in 
Perthshire we are merely illustrating the distribution of 
an isolated district, and that as we do not show the distri¬ 
bution in the areas north and south, east or west, of our 
county, our labour will to a great extent be in vain, since 
the area is not wide enough to yield sufficient data for a 
solution of the problem. To a certain extent this may be 
true, though (as I will presently try to show) we have in 
Perthshire many facilities for investigating the laws that 
govern distribution. We must remember, however, that 
the areas bounding us have or will have museums founded 
much on the same plan as ours, and that these, with ours, 
will afford the philosophic naturalist the material absolutely 
necessary for elucidating this and other problems. It is, 
therefore, clearly our duty so to form our Museum that it 
may, so far as is possible, contribute to an increase of 
human knowledge—knowledge not in the sense of mere 
education, but in the acquisition of new facts. 
I have said that Perthshire offers many facilities for the 
study of the laws which govern the distribution of species. 
A glance at the map, which I have here, will show that the 
physical features of the county are by no means uniform. 
The map shows the districts into which Perthshire has 
been divided. In the first place, we have two great sub¬ 
divisions, which correspond not only with the geological 
formations but with the mean altitude above sea-level. 
The smaller of these sub-divisions belongs geologically to 
the Old Red Sandstone formation, and is essentially the 
Lowland part of the county, very little of it attaining, much 
less surpassing, 1000 feet elevation above sea-level. The 
other and larger sub-division belongs to the Silurian forma¬ 
tion, and is the Highland part of the county, comparatively 
little of it being below 1000 feet elevation, and most of it 
considerably above that height. To speak more definitely, 
I may state that the county (or rather the area which for 
natural history purposes we call the county) contains 2457 
square miles. Of these about 743 belong to the Old Red 
Sandstone area, and 1714 to the Silurian. Of the Old Red 
Sandstone, or Lowland, area, about one-fifteenth only is 
above 1000 feet altitude, while of the Silurian not less than 
1329 square miles surpass this altitude. It is also worthy 
of note that, as may be supposed, the Lowland or Old Red 
Sandstone area is essentially the cultivated one, while the 
other is for the most part necessarily uncultivated. 
