SUNDRIES. 
227 
was essentially improved thereby. It obtained but little favor, 
although a century later his compound microscope, in practical 
construction, was better than the microscopes manufactured at 
that day. This surprising condition of affairs had its origin in 
the difficulty of uniting the lenses in such a manner that their 
poles lay in a parallel line. Grindl recognized this difficulty and 
overcame it. 
At the same period the compound microscope was still further 
perfected by Carl Anton Tortona, by means of a perforated ob¬ 
ject table, rendering the use of reflected light much more practic¬ 
able. Smaller lenses, with a narrow opening, could be used, so 
that greater magnifying power could be produced without using a 
stronger ocular or lengthening the tube of the microscope. With 
the power of 80 diameters of the past it was impossible to obtain 
pictures that were recognizable, which can accomplish at the pre¬ 
sent time with a power of magnifying 20 times so that it was now 
possible to obtain good results with powers of 2-200 diameter. 
This was acheived by Philippus Bonannus, who applied a me¬ 
chanical apparatus for changing the distance between the objec¬ 
tive and the object. 
Up to this time greater magnifying power by this microscope 
was produced by lengthening the tube, and thereby the distance 
between the objective and the ocular. Bonannus employed the 
use of three different tubes, each of which contained three bi¬ 
convex lenses. Bonannus used artificial light to illuminate by 
his instruments, although daylight was perfectly practicable. The 
artificial light was conveyed by means of a lamp through two bi¬ 
convex lenses. 
[To be coritinued.) 
SUNDRIES. 
HOGS IN THE UNITED STATES. 
The Commissioner of Agriculture furnishes the following sta¬ 
tistics of the number of swine in the United States, from which 
it appears that Iowa has stood foremost among the pork-pro- 
