17 
This launch, built by the Racine Boat Manufacturing Company, of Racine, 
isconsin, is 25 feet long by 6 foot beam and is licensed to carry seventeen 
persons. The machinery furnished with it was replaced during the summer 
| by a compound engine of four and a half horse power, with keel condenser. 
| Both boiler and engine were designed by Assistant Professor VanDervoort 
of the University department of mechanical engineering and the engine and 
the speed propeller were made under his direction at the University shops. 
The launch was not designed especially for speed, the distances to be covered 
/im our work being usually very short. It gives us, however, a rate of about 
six miles per hour. It is entirely safe in all weathers to which it may be ex- 
| posed in our situation—a point of special importance to us since our regular 
routine of field work must be carried out without reference to storm or tem- 
perature. Four skiffs of various sizes and a portable canvass boat complete 
the aquatic equipment. 
The more peculiar items of the field and laboratory appar atus are Hy: 
plankton equipment, the breeding cages for the aquatic insects, and a specially 
constructed centrifugal machine for the rapid precipitation and condensation 
in graduated tubes of the product of quantitative collections. This last is 
-amodification of the centrifuge used by physicians, the tubes and tube ear- 
‘Tiers being the same, but the mechanism being specially designed for us by 
Proressor VanDervoort and made under his supervision at the University 
‘shops. The plankton apparatus first used consisted of a peculiar conical net 
(Apstein pattern) made of No. 20 silk bolting cloth. This was hauled through 
the water obliquely from bottom to top, a distance of thirty metres, 
‘at a perfectly uniform rate, the movement being timed by seconds counted 
‘with watch in hand. The net was suspended to a carrier and drawn along a 
tightly stretched line, to which it was hung by means of pulleys, the various 
particulars of the arrangement being devised by Assistant Professor Smith, 
i charge of the plankton apparatus and the Station itself during the first 
‘year. In May, 1896, this plankton net was superseded by a hand force- 
‘pump, selected after considerable investigation of various styles, of a size 
and weight to be conveniently managed in a large skiff. The feed pipe 
of this pump is long enough to reach the bottom in our deepest water and 
ithe discharge pipe delivers into a straining net suspended in the water from 
a float to secure the contents of a vertical section. The further end of the 
feed pipe is sunk to the bottom and slowly raised to the surface, the pump 
being meanwhile worked by an assistant in a perfectly regular manner. 
‘Minor features of the apparatus and items of the procedure will be described 
in a special paper on our Station methods, now in course of preparation by 
the Station Superintendent. 
For keeping insect larvee under perfectly natural conditions but exposed to 
€ontinual observation small cubical boxes were used, with two sides and the 
bottom of wood and the other two sides of wire gauze, and a cover of glass 
Set in a wooden frame which overhung the top ‘of the case, fitting closely to 
the sides. These cases were placed around a large float in the lake or river in 
such a manner as to be kept about half full of water, which ofcourse had free 
access uae the wire gauze sides. 
t. aaa | 
