220 Scientific News. [February, 
Blue Emulsion—A slightly modified form of Thiersch’s for- 
mula: 
1. To 300°™ of melted gelatine add 120°™ of a cold-saturated 
solution of green vitriol (ferro-sulphate). 
2. To 600%™ of melted gelatine add first 240°™ of a saturated 
solution of oxalic acid, then 240°™ of a cold saturated solution of 
red prussiate of potash (potassic ferricyanide). 
3. No. 1 poured slowly into No. 2 while stirring vigorously; 
the mixture heated for fifteen minutes. py 
4. After cooling, the emulsion is pressed through netting, thi 
vermicelli washed and spread on waxed paper for drying. In ‘i 
case the vermicelli must be dried directly, as they do not melt w 
without the addition of oxalic acid. ld 
he dry vermicelli are prepared for use by first soaking in a 
water, and then heating with the addition of oxalic acid eno 
to reduce them to a liquid. Eoo liters ol 
Black Emulsion. — 1. Soak 500 g. gelatine in two pe 
water, in which 140 g. of common salt have previously 
dissolved, and melt the mass on the water-bath. _ we 
2. Dissolve 300 g. nitrate of silver in 1 liter distilled water. Z 
. No. 2 poured very slowly into No. 1 while stirring. hie 
tremely fine-grained emulsion may be obtained by us g 
times as much water in Nos. 1 and 2. 
4. No. 3 pressed into vermicelli as above, and t 
No. 5 by clear daylight. a engl ofa 
5. Mix 1% liter paap, potassic oxalate with 500 
cold-saturated solution of ferro-sulphate. k emulsion, 
6. No. 4 mixed with No. 5 gives a thoroughly blac d finally 
which should be washed several hours, again melted an 
poured in a thin layer on waxed paper. 4 pota 
A gray-black out may be obtained by using ee ig 
sic bromide in the place of common salt in No. 1, te 
operations being the same. 
hen mixed with 
A”, 
Ue 
SCIENTIFIC NEWS. 
pee! 
— The Trustees of Williams College engaged pe SPO Zoologi 
series of years, one of the tables at Dohrn’s Internatio opied by 
cal Station at Naples. It has until recently bo id ‘Scientific 
Dr. Edmund B. Wilson, a graduate of the Shefhe co 
School, and of the Johns Hopkins University. rinciples which | 
His occupancy of the table illustrates the ais A appoi"! 
already able by 
guished for research, may apply for the use of ye pillia 
