is now for the most part removed with a pipette from the tube c, the tube is freed from all moisture by means of a current of dry air produced by the water air-pump, and only then is the iron head-piece d cemented on with the finest sealing wax, in such a manner, that the tube c projects inside to some distance above the bottom, in order that later, the stopper bearing the scale may rest in the mouth of the glass tube c and not in the iron casing. The last filling with boiled mercury to the level y is performed by the aid of a capillary glass tube, in order to avoid all air bubbles on the sides of the tube.

In order to place the mercury thread in each experiment on one of the first divisions of the scale, it suffices to press the cork of the graduated tube, with a rotary movement, somewhat deeper into the mercury tube c, fig. 1. If the thread has thereby exceeded the commencement of the scale, there is a small brass weight, fastened on a thread and previously warmed by contact with the hand or tongue, sunk into the fluid a, fig. 1. If the weight of the brass weight be g grams, its temperature 1, its specific heat sm, the latent heat of melting for water 1, and the weight of melted ice, obtained by equation (2), which corresponds to an oscillation of one scale division, denoted by p, then the oscillation produced by the brass weight g is equal scale divisions. If we let

smtg

to

and g equal successively 0.1, 0·2, 0·4, 0·6,

p=0·000853

grams, the

following retreats of the mercury thread, expressed in round

numbers, will be obtained.

By dipping in one of these brass weights, previously warmed under the tongue, the mercury thread can be made to retreat to the desired extent. The oscillations corresponding to the little weights, which were only warmed to 37° C., are well adapted to give an idea of the extraordinary delicacy of the instrument. The increase of temperature which 04 grams of brass at 37° C. would produce by immersion in the mass of water in the instrument, amounting to about 20 grams would displace the mercury thread of a centigrade thermometer only 0007, that of the just described calorimeter, however, twenty scale divisions, each of which was, in the instrument employed, one millimeter in length.

In relation to the readings on the scale, it is still to be observed that, before such observation of the scale tube, which is best to be made with the telescope, the former must, particularly when it is very narrow, be gently agitated by repeated rapping until

the capillary resistance is overcome, and the mercury thread does not retreat by further rapping.

Table 1 shows already that the mercury thread of the instru ment is generally not perfectly stationary. The displacement, which, in a positive as in a negative sense may amount to 1 to 3 divisions in the hour, is, as the observer may easily perceive by the employment of the calorimeter, nearly proportional to the time. The slight error thus introduced may be eliminated in the following manner: As soon as it is seen that the nstrument has become sufficiently stationary, the height of the mercury thread is noted from 30 to 30 minutes. If the displacement of the latter amounts in m minutes to 70 scale divisions, then the displacement to be ascribed to foreign influences is for one minute

Το

mo

The hour M, and the height of the mercury thread Qo are now observed at the moment, when the substance to be investigated is allowed to fall from the heating vessel ƒ, fig. 4, (see page 173) into the calorimeter vessel a, fig. 1, and both observations are repeated one hour later, whereby further M, and Q result; finally the movement of the mercury thread indeper dent of the heat to be measured, is once more determined, as in the beginning of the experiment

ΤΙ

m1

The mean displacement of the mercury thread, independent of the experiment, amounts therefore in one minute to

scale divisions.

This value is to be added to the oscillation o the mercury thread Qo-Q, observed during the experiment a a correction, and especially, with the negative sign prefixe when the displacement independent of the experiment tool place in the way of ice melting, with the positive sign in th opposite case. For the oscillation T, corresponding to the quan tity of heat to be measured, the equation

is therefore obtained, wherein it is hardly necessary to mer as that, for the direct readings, their values according taly table of calibrations are to be substituted.

(To be continued.)

Ъ

T. XLIII.-On the Solar Protuberances; Abstract of a Note read y Prof. L. RESPIGHI, before the Accademia de' Nuovi Lincei, Dec. 4, 1870.* With a plate.

HIS note is founded upon spectroscopic observations of the Her and protuberances of the sun regularly made by Prof. spighi, at the Campidoglio observatory in Rome, from Oct., , to Nov., 1870. The author deduces some important facts ative to the forms, size, development, and transformation of protuberances; to their duration, and the manner of their ibution over the solar disk; and to their connection with other solar phenomena, namely, the spots and the faculæ. nong the surprisingly various and singular forms of the berances, he finds those that have the appearance of gaseous ses issuing from the sun's surface to be so marked and conthat it is necessary to conclude that they are really proby gaseous eruptions from within the body of the sun, -place with more or less energy, and o. a varying scale deur.

being able to explain the various modes according to neh the erupted masses are ramified and diffused, by refer them to the simple velocity of eruption combined with the of gravitation, and with the natural expansion of the jets, tre resistance of the solar atmosphere, or on the supposi powerful currents in the latter, he finds it necessary to e concurrence of other forces acting within the erupted and between these and the body of the sun.

f ard to the dimensions of the protuberances, spectroservations show that they may vary between the most mits, from jets which are very small and low, to those ous section and of immense altitude. Among the ences sketched by Prof. Respighi, which exceed 4,000, * more than 700 not less than 1' high, that is, more than 3 the diameter of the earth in altitude, and among not less than 6', that is, more than 20 times the neter in height.

immense altitudes of the protuberances, correspond, ite expansions or ramifications in a horizontal direc are truly astounding, and in which the hydrogen difin vast volumes, or stretches out in branches fe or less subtile and of enormous length.

On of Respighi observes that the loftiest protuberances llined by him show, besides the spectral line C, which is very In rislated for this Journal, by Prof. ARTHUR W. WRIGHT, of Williams Colat Williamstown, Mass., from Secchi's Bull. Met., Rome, Dec. 31, 1870. e. Jotk. SCI.-THIRD SERIES, VOL. I, No. 4.—APRIL, 1871.

distinct, also the line F, and the yellow line D3,* to their very summits, a fact already remarked by him in a previous note.

The development of the protuberances is ordinarily announced by bright points or patches standing out upon the chromosphere (strato rosato), from which subsequently burst forth jets more or less subtile, which rise, sometimes slowly, sometimes rapidly, to considerable elevations, and then fall back in parabolic forms upon the sun, or diffuse themselves in masses of varying and sometimes very singular conformation, and subject to more or less rapid transformations. Prof. Respighi has been able now and then to be a witness of the development, in the neighborhood of the spots, of enormous protuberances, produ ced by the eruption of groups of very slender and brilliant jets, which in a short time spread into great cloudy masses, either settling down upon the surface of the sun, or gradually vanishing at a great height above it. An example of this kind of eruption is given in the plate, in the figure of the protuberance No. 14, observed October 29, 1870.

Respecting the duration of the spots, it is found that while some of them are developed in the space of a few minutes, and, after undergoing rapid transformations, in a few minutes thin out and disappear, others remain visible for a long time, sometimes retaining in their forms some characteristic traits. Those which are the most variable and evanescent, are produced in the neighborhood of the spots. Outside the zone of spots, up to about 70° in latitude, the protuberances commonly remain visible for many days, so that it is possible to follow by them the rotation of the sun; and it has been possible, in the course of the observations, to observe the passage of some of the protuberances from one border of the sun to the other, and also their return to the first border, after having made a com plete revolution. The time of the sun's rotation as deduced by means of the protuberances agrees very closely with that obtained by observation of the spots near the equator; which shows that the retardation of this rotation observed in the spots distant from the equator, is an appearance due to the proper motion of the spots themselves.

In regard to the distribution of the protuberances upon the solar surface, Prof. Respighi finds the results deduced from the earlier observations confirmed, namely, that in the circumpolar regions, within a distance of 20° from the poles, the

This is doubtless the line observed by Mr. Lockyer, Oct. 20, 1868. In a communication to the Royal Society made that year, he says, speaking of the observation of a solar protuberance, "two of the lines correspond with Fraunhofer's C and F; another lies 8° or 9° (of Kirchhoff's scale) from D toward E. *** It is remarked that the line near D` has no corresponding line ordinarily visible in the solar spectrum. See also Mr. Lockyer's account of the recent eclipse (from Nature; this Journal, III, i, 229) where this line is attributed to a new element, a deduction first made we understand by Prof. Young.

A. W. W.

protuberances are either not found, or occur only exceptionally; though notwithstanding this, the surface of the sun in these regions cannot be in a condition of perfect calm; for the appearance of small jets, and the irregularity and variability of the chromosphere, show that even in those regions there is a state of continuous eruption, though on a very small scale.

Considering the whole body of observations made, it appears that the northern hemisphere is perceptibly more characterized by great protuberances and gigantic eruptions than the southern, and that in the former large protuberances are on rare occasions seen at distances less than 20° from the pole, a thing which never happens in the southern hemisphere. In the vicinity of the equator, protuberances of great size occur less frequently than in higher latitudes.

As to the connection of the protuberances with the faculæ, it is found that the latter are commonly accompanied by protuberances of considerable size, though without being confounded with them in the same phenomenon. Thus it would appear to be proved that the faculæ are special modifications of the photosphere in the neighborhood of powerful eruptions.

The following results have been deduced from a great numFor of observations made upon the border of the sun's disk, in the region of the spots :

1. In the neighborhood of the spots the chromosphere (strato rosato) is rather low, quite regular and intensely bright.

2. Upon the exact locality of a spot, or rather over its nucleus, the chromosphere is generally very low and sometimes totally wanting.

3. At the nucleus, either there are no eruptions or they are confined to jets of great subtilty and little duration.

4. The nuclei of the spots are either totally obscure or possess very feeble luminosity.

5. Along the borders of the spots, jets are thrown up of extraordinary intensity and violence and of very definite configuration. 6. The jets adjoining the spots consist not solely of hydrogen, but also of other substances, as is shown by their respective bright lines in the spectrum.

7. Among these bright lines which are commonly found at the base or in the lower portions of the jets, there are frequently seen those of sodium, magnesium, iron, &c., and constantly two lines in the re, one between C and B, distant from C of the space C-B the other is between B and a, distant from a of the space B-a. These lines do not correspond with those of any substance yet known. They are also not infrequently seen quite bright in the highest parts of the jets.

8. Now and then the eruptions in the vicinity of the spots assume gigantic proportions, and are probably the cause of the