The balloon carries two collectors a given vertical distance apart.
During the pre-Linnaean period, the beauty of insects - especially the Lepidoptera - had attracted a number of collectors; and these "Aurelians" - regarded as harmless lunatics by most of their friends - were the forerunners of the systematic students of later times.
That doctrine took some few years to produce its effect, but it became evident at once to those who accepted Darwinism that the natural classification of animals, after which collectors and anatomists, morphologists, philosophers and embryologists had been so long striving, was nothing more nor less than a genealogical tree, with breaks and gaps of various extent in its record.
There are also a deputy postmaster-general, chief superintendent and four superintendents of telegraphs, a chief collector of customs, three collectors and four port officers, and an inspector-general of jails.
The height of the walls in the various observatories, the height of the collectors, and the distance they project from the wall vary largely, and sometimes electrometer, and they sometimes leave hardly a trace on the photographic paper.