430 
(4) Professor L. E. Dickson; ‘Concerning 
real and complex continuous groups.’ 
(5) Professor E. O. Lovetr: ‘ An application 
of continuous groupstonon-euclideangeometry.’ 
(6) Professor E. O. Loverr: ‘ Contact trans- 
formations which change asymptotic lines into 
lines of curvature.’ 
(7) Professor H. B. Newson: ‘ Indirect cir- 
cular transformations and mixed groups.’ 
(8) Mr. W. B. Fire: ‘On metabelian groups 
that cannot be groups of cogredient isomor- 
phisms’ (preliminary communication). 
(9) Dr. EDwARD KasneR: ‘On algebraic po- 
tential curves.’ 
(10) Professor MAxIME BécHER: ‘Green’s 
functions in space of one dimension.’ 
(11) Dr. H. E. Hawxes: ‘Estimate of Ben- 
jamin Peirce’s linear associative algebra.’ 
(12) Dr. G. A. MILLER: ‘On holomorphisms 
and primitive roots.’ 
(18) Dr. EDWARD KAsNER: ‘Theorems on 
collinear lines in space.’ 
(14) Mr. C. W. M. Brack: ‘ Decomposition of 
a form in m variables in an arbitrary domain 
with respect to a prime ideal modulus.’ 
(15) Professor Maximm Bocusr: ‘An ele- 
mentary proof of a theorem of Sturm.’ 
(16) Dr. L. P. EisENHART: ‘Surfaces whose 
first and second fundamental forms are the 
second and first respectively of another sur- 
face.’ 
(17) Dr. L. P. Eis—ENHART: ‘ Possible triply 
asymptotic systems of surfaces.’ 
(18) Dr. H. F. Srecker: ‘On the determi- 
nation of surfaces capable of conformal repre- 
sentation upon the plane in such a manner 
that geodetic lines are represented by algebraic 
curves.’ 
(19) Professor MAXIME BécHER : ‘ Non-oscil- 
latory linear differential equations of the 
second order.’ 
The next regular meeting of the Society will 
be held on Saturday, April 27th. The Chicago 
section will meet at the University of Chicago, 
on Saturday, April 6th. F. N. CoLe, 
Secretary. 
THE ACADEMY OF SCIENCE OF ST. LOUIS. 
AT the meeting of the Academy of Science of 
February 18th, 1901, 23 persons present, Pro- 
SCIENCE. 
(N.S. Vow. XIII. No. 324. 
fessor J. L. VanOrnum read an address of gen- 
eral interest, summarizing the progress made 
in engineering during the nineteenth century. 
A paper entitled ‘Florida lichens,’ by Pro- 
fessor P. H. Rolfs, was presented by title. 
Professor F. E. Nipher showed two photo- 
graphic negatives, developed by an ordinary 
pyro developer. One plate had been exposed 
in a printing frame for 1,000 seconds at a distance 
of a meter from a 300-candle lamp. It was 
then treated for ten minutes in a chromic acid 
bath having ten drops of an eight-per-cent. solu- 
tion of chromic acid to three ounces of water. 
This treatment was in the dark-room. The 
plate was then developed in the dark-room. 
The exposure of the other plate had been 
equivalent to a tenth of a second at the same 
distance from the lamp, and was exposed under 
the same plate. This plate developed normally 
in a pyro developer, having six drops of bro- 
mide and six drops of potassium ferro cyanide, 
both in ten-per-cent. solutions. The over-ex- 
posed plate showed more of detail, but the con- 
trasts were less strong than in the plate with 
normal exposure. It looked like a slightly 
under-exposed plate. 
When a plate with this exposure is treated 
with the chromic acid bath while in the light, 
and is then developed in the light, a positive 
picture results. The chromic acid bath may 
be replaced by ten drops of saturated potas- 
sium bichromate solution, and four drops 
of common C. P. nitric acid, to three ounces 
(90 cc.) of water. Thereis reason to believe 
that any camera exposure which was intended 
to be correct may be developed as a positive in 
the light by such methods. It is certain that 
it may be handled as a negative in the dark- 
room. f 
Professor Nipher stated that if either a nega- 
tive or a positive had been started and had re- 
sulted in a failure, due to improper treatment, 
the picture with the fog on the plate might 
be chemically destroyed by chromic acid, and 
the picture might be redeveloped in either case 
either as a negative in the dark-room or as a 
positive in the light. 
It was also stated that one plate had been 
developed as a superb negative at a distance of 
a meter from a 300-candle lamp. This case was 
