wt a sie ed ed ee 
NATURE | 
235 
Hemispherical excess. 
ort South. 
+4180 eat 
(+ 40) 
+2580 
— 2920 
+ 920 
—1420 
+ 1000 
— 2480 
+ 120 
+1320 
+1050 
— 1400 
From these we derive the following values of a period of 
oscillation by taking the differences in dates between the positive 
extremes :— 
"27 days, 21 days, 29 days, 30 days, 22 days—mean, 25'8 days ; 
while doing the same with the negative extremes, we obtain :— 
24 days, 22 days, 31 days, 17 days, 32 days—mean, 25:2 days. 
5. The second of the three periods extends from the end of 
June to the beginning of November 1860. Treating this in the 
same manner, we obtain :— 
Hemispherical excess. 
Date. North. South. 
F; MHOC uly Li) fos cac.secenas es + 4900 
ae Ui 2S ee ao — 600 
July 30 ... . +2040 
Aug. 9 ... <t —2400 
Aug, 21... . + 400 
Sepe's” :.. oh - 1400 
Sept. 16... - + 400 
Oct. 1 = —1180 
Orie +. . + 800 
Ock 9. « — 2560 
Or oie | ee : ...(- 380) 
From these we derive, by taking the differences in dates of 
the positive extremes, 
29 days, 22 days, 26 days, 23 days, 22 days—mean, 24°4 days ; 
while doing the same with negative extremes, we obtain :—- 
18 days, 27 days, 26 days, 18 days—mean, 22°25 days. 
6. The third of these three periods extends from the beginning 
of May.to the end of August 1862. Treating this in the same 
manner, we obtain :— 
Hemispherical crea 
Date. North. jouth, 
1862, May 9 + 6co 
May 22 .... —1160 
June 3... +2960 
June rs .. — 2600 
June 29 +1880 
July 16 — 800 
July 26 + 2400 
Aug. 14 — 200 
Aug. 23 + 460 
Taking, as before, the distances between the positive extremes, 
we obtain :— 
25 days, 26 days, 27 days, 28 days—mean, 26°5 days ; 
while from the negative extremes we obtain :— 
24 days, 31 days, 29 days—mean, 28°0 days. 
From the whole three periods we obtain, as the most probable 
mean value, 25°2 days. 
7. We do not profess to have discovered the cause of these 
oscillations, but we would nevertheless suggest that the obser- 
vational facts here brought to light may perhaps be connected 
with two other observational facts, the one of which was first 
brought to light by Carrington, and the other by ourselves. 
The first of these is the fact that, generally speaking, spots in 
the north hemisphere have much about the same latitude as those 
occurring at the same or nearly the same period inthe south, both 
sets widening or contracting together. We may perhaps, there- 
fore, suppose, by applying this law, that the latitude of the spots 
which cause the positive extremes in the above series is not 
greatly different from that of those which cause the corresponding 
negative extremes. 
The second observational law is that which tells us that spots 
about the same period have a tendency to attain their maximum 
4 
at or near the same ecliptical longitude. Now, if we suppose 
that in the foregoing three series the greatest positive extremes 
were caused by the positive spots attaining their greatest size, 
and the greatest negative extremes by the negative spots, 
attaining their greatest size, it would follow that the two sets, 
positive and negative, must have taken their rise at places on 
the sun’s surface 180° of longitude different from each other 
inasmuch as the one set about twelve or thirteen days before or 
Bier passed (let us say) the same ecliptical longitude as the 
other. 
But if the positive set have the same latitude as the negative, 
and if the one is 180° of solar longitude different from the other, 
it would mean that the two outbreaks are at opposite ends of the 
same solar diameter. 
This conclusion is an interesting one, but, of course, it 
requires to be verified by further observation before it be finally 
received. Meanwhile, we are engaged in mapping out syste- 
matically the positions of the various outbreaks of the sun’s 
surface, and we shall soon, therefore, be able to find whether 
or not there be any truth in this conjecture. 
Geologists’ Association, July 4.—Mr. Henry Woodward, 
F.R.S., president, in the chair.—1. “A sketch of the Geology 
of Northamptonshire,” by Samuel Sharp, F.S.A. A general 
section of the county of Northampton shows the lias as a 
basal formation with the inferior oolite beds of the ‘‘ Northamp- 
ton sands” above. Fossils are abundant, and some species are 
not found in other localities. The upper division consists of a 
nearly white siliceous sand with bands of clay and a plant bed, 
the whole of these deposits being evidently of estuarine and 
littoral origin. Above these, but unconformably, lies the 
bed classed as Great Oolite, and which consists of, firstly, 
a series of clay beds with a ferruginous base and containing 
a plant bed; then, secondly, a limestone series abounding with 
fossils and affording an ornamental stone called ‘‘ Alwalton 
marble.” The bed of clay reposing on these great oolite strata 
may be considered the equivalent of the ‘‘ Bradford clay,” and 
still higher in a general section will be found the Forest marble, 
the Cornbrash, and, highest of the secondaries, the Oxford clay. 
The high lands of the county are frequently capped by boulder 
clay and glacial gravels containing fragments from nearly the 
whole series of the primary and secondary rocks. <A peaty 
fluviatile bed above the gravels contains at its base numerous 
remains of mammalia. The lias extends throughout the county 
though appearing only in the valleys, the iron sands occupy the 
middle and the Lincolnshire limestone the northern portion of 
the county, while the other formations are patchy in extension. 
A high table-land about Naseby gives rise to the Avon, the 
Welland, and the Nene, which occupy the principal valleys of 
the county. In past times efforts were made at consider- 
able cost to find coal,.and recently the question of whether 
coal can be obtained in the county has been discussed, 
but judging from what we know of the rocks of 
the nearest coal-field of Warwickshire, and of the intervening 
district, as much as 4,500 ft. of strata may lie above coal-seams 
of sufficient thickness to be worked. Moreover, Prof. Hull, 
F.R.S., concludes that ‘* Carboniferous ” coal will not be found at 
any depth in Northamptonshire. —2. ‘On some new Crag Fossil,” 
by Alfred Bell. The author’s observations since his former 
paper on the crags was read, confirm the views he then expressed 
as to the divisibility of the English crags into four divisions 
founded on palzontological evidence. He had determined 145 
species (some new, some new to the crag, and some new 
to particular divisions) in addition to those given in his 
published lists. —3. ‘‘An account of the Eruption of Mount 
Vesuvius of April 1872,” by J. M. Black. In this paper 
the brief but violent and destructive eruption of last year was 
described by the author, who has carefully noted the various 
phenomena that occurred during its continuance. An ascent of 
the yoleano was made by Mr. Black, a few days after the 
eruption, and the form and condition of the crater observed. 
The author had succeeded in photographing various parts of 
the mountain after the eruption, and the views so taken were 
exhibited. 
PHILADELPHIA 
Academy of Natural Sciences, April 1.—Dr, Ruschena 
berger, president, in the chair. The following paper was presented 
for publication :—‘‘ On the Affinities of the Sirenians,” by Theo: 
Gill. Prof. Leidy remarked that the rat presented this evening 
by Mr, L. Fussel was a specimen of the Black Rat, or Aus rats 
