80 
rods, and are provided with pinions, cranks and binding screws to make 
accurate adjustment. The stand is provided with castors so adjusted that 
it may be thrown on or off its legs with the foot. AIl the handles are 
nickel-plated and the whole apparatus enameled black. 
With this apparatus it is possible to work in the vertical or horizontal 
position or at any inclination. The adjustment is easily and quickly 
made by loosening the binding nut between the friction plates and turn- 
ing the bed plate to the desired position. The bed plate can be rotated on 
the horizontal axis to get the advantage of room and direction of light 
without moving the stand upon its legs. When the bed plate is turned to 
the horizontal the top of the bed plate is 33 inches from the floor; too low 
“to work with comfort. By raising the elevating post the bed plate may be 
carried up to the height of five feet. This adjustment makes it possible 
to always have the work at a comfortable height, either in the sitting or 
standing position, and regardless of the stature of the operator. 
The apparatus has been used for some months in the Veterinary Lab- 
oratory of Purdue University. A Zeiss microscope and a long-focus premo 
camera are mounted upon the carriages (any other microscope and camera 
can be mounted as easily), and photographs have been taken of parasites, 
histological sections and bacteria. It has been used in all positions, with 
fresh and permanent mounts, and the results are entirely satisfactory. 
The stand was built by C. W. Meggenhoffen, of Indianapolis. 
Aw Lyrrnite System or Forms, SATISFYING THE REQUIREMENTS OF HILBERT’S 
Law. By J. A. Miner. 
Let Z represent the totality of homogeneous integral forms of four variables 
(excluding those which vanish identically) which are unchanged by the group 
of linear substitutions generated by the operators. 
Ae hs iy aig lid RMN ka ne 
Vi SS Z, = —& Z, 
ZF Li Zig ag 
Lys Ly L, = —Z, 
9 _ 
Where «=e a 
