48 
February 1.—On the hydrogenic protuberances of the sun, 
observed at the Royal Observatory of the College of Rome 
in 1884.—Prof. Tacchini, in continuation of his previous 
note to the effect that 1884 must be considered as a year 
in which the phenomena of the chromosphere had attained 
their maximum development, presented the results of ob- 
servations made by him on 242 days. From these it ap- 
peared that the number of the protuberances increased from 
March to October. In order to get rid of the anomalies which 
are met with in various observations, and to obtain a curve 
representing the course of the phenomena in the quinquennial 
period 1880 to 1884, Prof. Tacchini has taken as monthly means 
the means of three months, considering each month along with 
the month before and after it. The curve so constructed shows 
three culminating points or periods of maximum activity, these 
corresponding to July, 1880, September to October, 1881, and 
March, 1884, which last is the highest in the whole series. The 
maximum of the protuberances follows that of the sunspots, and 
recent observations make it probable that 1885 will be a year of 
greater activity in the chromosphere and solar atmosphere. —On 
the degree of precision in the determination of the density of 
gases. Dr. Agamennone stated that the first to experiment 
with a certain amount of success on the density of gases were 
the physicists Dumas and Boussingault, and that Regnault had 
introduced the most important improvements in the methods of 
working adopted by them. He observed, however, that even 
these improved methods of Regnault were not exempt from certain 
errors, the nature of which the author pointed out and described, 
indicating the precautions that had to be used in the various 
operations of weighing, in order to avoid some of these errors 
by taking advantage of the accurate instruments which we possess 
at the present day. The author insisted specially on the con- 
stant source of error proceeding from the property which glass 
has of condensing gases on its surface, and on the exactness of 
measurement required in determining the pressure at which the 
gas to be weighed is contained in the vessel in which the weigh- 
ing is effected. Dr. Agamennone has repeated in the Royal 
Physical Institute of Rome all the experiments of Regnault, and, 
correcting an error found in one of the experiments of that 
physicist, he finds that for the value of the weight of a litre of 
air, which, according to the corrections made by Kohlrausch 
and Lasch, would be 1°292756 grammes, there ought to be 
substituted 1°292767 grammes—a determination which, accord- 
ing to Dr. Agamennone, is subject to a maximum uncertainty 
of about + o'0005 gramme, and to a mean uncertainty of 
+ 0'000067 gramme.—Determination of the density of the air. 
Dr. Agamennone having in his previous paper shown how 
in the determination of the density of gases the errors 
affecting the final result proceed from the measurements of weight 
and pressure, announced that he had executed two series of ex- 
periments for the determination of the density of the air, making 
use of weights and pressures separated from one another by 
pretty wide limits. The pressures employed in the two series of 
experiments were : (1) that of the atmosphere ; and (2) one of 
two atmospheres. The author, after describing his methods of 
procedure and the precautions taken by him, communicated his 
results, which showed a great difference between the mean 
values of his two series, and that because the air under pressure 
departs from Mariotte’s law. Dr. Agamennone concludes that 
when the density of a gas is to be determined, the gas being 
weighed in a compressed state, it is necessary above all to know 
by direct experiments the variations in volume of the gas 
operated on, and to know what amount of condensation there 
NATURE 
is on the walls of the vessel in which the gas is com- 
pressed. For the determination of the deviation of a gas from 
Mariotte’s law, which is a matter of so much importance in 
researches of this kind, the gas might be weighed at different 
pressures in a resisting vessel with a sufficiently delicate balance. 
Some experiments of Regnault have shown this method to be 
sufficiently satisfactory.x—Consequences of a new hypothesis of 
Kohlrausch on thermo-electric phenomena. Dr. Battelli, after 
giving a vésumé of the theoretical explanations offered by Thom- 
son and Tait to account for the results obtained experimentally 
in thermo-electric phenomena, stated also the hypothesis of 
Kohlrausch on the electrical transport of heat, and showed how, 
from the conclusions of Kohlrausch, all the formule confirmed 
by experiment might be deduced.—Other communications :— 
Drs. Ciamician and Silber have continued their studies on the 
compounds of pyrrol, and explained minutely the method by | 
which they had succeeded in conyerting pyrrol into pyridin,— } 
[May 14, 1885 
Prof. Cassani communicated a paper on the angles of linear 
spaces.—Dr. Tonelli presented a note on the analytical repre- 
sentation of certain singular functions.—An abstract was com- 
municated of a memoir by Messrs. Vanecek, entitled ‘‘Sur la 
Génération des Surfaces et des Courbes gauches par les 
Faisceaux de Surfaces.” 
February 15.—On the worship of stone weapons in the 
Neolithic age. Signor Pigorini exhibited a singular flint imple- 
ment which had been found in one of the caves in the commune of 
Breonio Veronese, referred to the Neolithic age. It has the 
triangular form of a lance- or arrow-head, but is of rather large 
dimensions. It weighs, in fact, 1°710kilo., and one of the equal 
sides of the triangle is more than 21 cm. in length. It cannot 
be supposed that this colossal spear-head could have been used 
as a weapon, chiefly because its dimensions would have required 
a shaft of quite unmanageable size, but also because the cavity 
at its base would have rendered the shafting extremely fragile. 
Signor Pigorini called to mind how, even at the present day, the 
common people attributed a celestial origin to the weapons of 
stone —a superstition which also existed among the ancients ; but 
there are proofs that at the very time when these weapons were 
made they were held as emblems of divinity. There was, in 
fact, in the Neolithic age, a worship of the axe, since specimens 
of that weapon are found, of dimensions so small or so large, 
like that of Breonio Veronese, that they cannot be regarded as 
anything else than votive offerings.—Concerning a fragment of 
a manuscript of Cicero belonging to the ninth century. Signor 
Narducci found, in the Vatican Library, a valuable manuscript 
containing numerous Ciceronian fragments coMected by a certain 
Hadvardo. Signor Narducci transcribed the manuscript page 
by page, in the hope that, by collating it with the works of 
Cicero, now known, he might find some fragments‘of lost books 
of the great orator. After identifying each of the fragments, he 
found that the compiler had not had at his disposal any of the 
works of Cicero known in the Middle Ages, but not at the present 
day. Signor Narducci gave a short specimen of the manuscript, 
with the various readings found at the present day in the most 
esteemed versions of the various works of Cicero, and he 
announced that Prof. Schwenke is preparing a critical study of 
the manuscript in question. 
CONTENTS PacE 
Sir William Thomson’s ‘‘Mathematical and Physical 
Papers.” By. Prof. Helmholtz, F-R'S) 5295 23925 
Our Book Shelf :— 
Warren's °*Paradise Found” — --) <)pe-0 See 
Buxton’s ‘‘ Epping Forest.”—G. S. Boulger ... 28 
Jagnaux’s ‘‘Traité de Minéralogie appliquée aux Arts, 
a l’Industrie, au Commerce, et 4 |’ Agriculture, &c.” 28 
Letters to the Editor :— 
Photographing the Aurora Borealis.—Carl Siewers. 29 
Speed! and Velocity.—B. . .). W. ossi icine neeme 
Time.—Thunderbolts.— Vision.—Sunglows.—Antoine 
d’Abbadie a): sw le bajo iS See EE 
Plutarch on Petroleum.—W. H. Deering ..... 29 
Hut Circles.—Worthington G, Smith. ..... 29 
A Lady Curator.—Consul E, L. Layard. .... 30 
Hoar Frost.—Mrs, Caroline W. D. Rich 3 BO 
Rainbow Phenomenon.—Charles Croft. ..... 30 
Five: Mathematical) Rarities. =. 2.) eee 
On certain Spectral Images produced by a Rotating 
Vacuum-tube, By Shelford Bidwell ...+.. 30 
Jupiter. By W. F. Denning. (J/lustrated)..... 31 
Notes MORBPECOEr oo doc. EE 
Our Astronomical Column :— 
The Harvard College Observatory, U.S...... +. 37 
Tempel’s Comet (1867) 11.) = <<. s2) toa) one 
New Nebule: ss 66 6 @ 3 3° 2) = (see 
Astronomical Phenomena for the Week 1885, 
May 17-23) ew het seen oe) a 
The Iron and SteeliInstitute . 5:9. 2. 2). seme 
Sunlight and the Earth’s Atmosphere, II. By Prof. 
S. P. Langley. ((/ustrated) 1). 0- | «11-1 en 
Zoological Research, . 5s ye) is © «seen 
University and Educational Intelligence ..... 44 
Scientific Serials a Tae eDiets ais: celle Steet 
Societies and Academies ......: . «ss % 45 
