The use of the flattened burner is not fully appreciated; its advantages are, that there is no cold point in the flame, and the burner can be brought much nearer to the object to be heated, within 20 to 25 millimeters for the small sized burners. In this burner as usually made, the opening is too broad, experience having convinced me that a slit 2 millimeters across and about 40 millimeters in length is the most effective one for a small size burner, consuming about 5 cubic feet per hour; this burner is represented in fig. 1, which can be used with the ordinary tube, by detaching the tube with the flattened orifice.

By taking a burner of this description and putting two pieces on each side of the center, as represented in fig. 2, a very effi

cient burner is made for heating platinum crucibles in silica fusions, &c., and with such a burner, consuming 5 to 6 cubic feet of gas per hour, I conduct most effectually all silica fusions in one hour or less, taking care to protect the crucible from the current of the air by a properly constructed short conical chimney, which chimney can be made of soap stone, sheet

iron, or any other convenient material.

As was stated in the commencement of this article, it was not intended to describe the more complicated methods of burning gas in furnaces and by means of a blast, but to confine the remarks to the simpler forms in every day use, which can be made to accomplish all the requirements of the usual laboratory operations, and when a higher heat is required, the furnace must be our recourse, whether burning gas, charcoal or coke. The burner represented in figure 2 is the one I now employ in heating the crucible in my method of alkali determination with carbonate of lime and sal ammoniac, which method, with its more recent modifications, will be published in a very short time. The description of it, with all the minute details of manipulation, being ready for the press.

ART. XXXV.-On the connection between Terrestrial Temperature and Solar Spots; by CLEVELAND ABBE, Director of the Cincinnati Observatory.

WE are indebted to Sir Wm. Herschel for the suggestion that probably the presence of numerous spots on the surface of the sun is indicative of increased chemical activity, and is accompanied by increased radiation of heat. The investigations and theories of the past ten years however would lead us to an opposite conclusion from that of Herschel.

Immediately on the receipt of the Astronomische Nachrichten containing Wolf's tabular view of the relative frequency of the solar spots for the past three centuries, I made an extended comparison of the numbers therein given with such meteorological tables as were then accessible to me. After much labor I was forced to conclude that the variations of solar heat are so slight that they are masked in the local climatic peculiarites.

On further reflection, however, it seemed certain that the heat radiated from a dark spot should be of low intensity, and would therefore be largely absorbed by the aqueous vapor of our own atmosphere as well as by that of the sun. I have therefore been lately led to make a special study of the series of observations made on the Hohenpeissenberg, and published in the supplementary volume I. of the Annals of the Munich Observatory. This series specially deserves attention because of the remarkable uniformity of the circumstances under which the observations were made; it extends from 1792 to 1850, omitting the years 1793, 1799, 1811, 1812 and 1817.

*

Assuming that the number of visible solar spots or groups are an index of the existing solar radation of heat, we have but to compare the number (s) expressing the relative spot frequency as given by Wolf with the mean annual temperature, (4) as given by Lamont. The solution of the equation t=to+st gives us to and, which latter is the coefficient of solar spot influence on the radiation of heat.

The accompanying table exhibits for each year the value of s and t-the latter expressed in degrees of Reaumur. The arithmetical mean of the annual temperatures gives M1 +5°178+0°.061

prob. error of one annual mean ±0.449

The residuals are given in the column t-m

Introducing the term st we find by the method of least squares (4)=+5°•450(±0°·086)—s×0°·00789(±0°·00204) p. e. of one annual mean =+0°•430.

Volume VII, containing the continuation of this series has not yet been received.

AM. JOUR. SCI.-SECOND SERIES, VOL. L, No. 150.-Nov., 1870.

The residuals are given in the column -(t1).

That the probable errors are on the whole very little diminished, is owing to the presence of a few large discordances; on the other hand, the small probable error of the coefficient of s would indicate that it has a real existence.

As the daily 2 P. M. observation may be supposed to show with special clearness the direct heating power of the sun, I have sought for a confirmation of the preceding results by applying the same formula to the annual means of the temperatures observed at this hour.

The annual mean temperature at 2 P. M. is given for each year in the column t2 of the accompanying table. The arithmetical mean gives

M2+6°830+0°.067

p. e. of one annual mean = ±0°489

The solution for the co-efficient of s gives

(t)=+7°·108(+0°·100)-sx0°·00801(±0°·00221)

=

p. e. of one annual mean ±0.465.

This result therefore corroborates the former in indicating a ease in the amount of heat received from the sun during e prevalence of spots-a result clearly in harmony with the recent investigations into the nature of the solar photosphere.

The reality of the existence of the above coefficient of s will be rendered more striking to the eye if the mean of several years' observations is taken at the period of maximum and minimum spot frequency.

It would be interesting to seek in the above residuals for evidence of other temperature periods than that dependent on the eleven year spot period. There are indeed plain indications of such a period of about fifty or fifty-five years duration― probably identical with Wolf's fifty-six year period—but our series of observations is not extended enough to justify any exact conclusion.

If we acknowledge the probability of a connection between. planetary configurations and solar spots, then we are at once led to make a direct connection between the former and the temperature variations. Such an investigation I have begun and the indications are that positive results will be attained, and such as will demonstrate that the solar spots are but an imperfect index to the periodic changes in the solar radiation; these periodic changes being apparently more intimately and directly connected with the tides in the cool atmosphere surrounding the solar photosphere. The results of this investigation will be made known so soon as the recent observations on the Hohenpeissenberg can be incorporated into the work.

Cincinnati, July 20, 1870.

ART. XXXVI-On a new method of determining the Level-error of the axis of a meridian instrument; by C. A. YOUNG, Ph.D., Professor of Natural Philosophy and Astronomy in Dartmouth College.

[Read at the Troy meeting of the Am. Association for the Advancement of Science ]

THE inclination of the axis of a meridian instrument to a horizontal plane has hitherto been measured by three different methods: by the use of the spirit level; by examining with a collimating eye-piece the image of the wires as in nadir-point observations, the collimation having been previously determined either by reversal of the instrument or by collimators; and lastly by observing the transits of stars by reflection from an artificial horizon.

The first of these methods is by far the most used, and with portable instruments is sufficiently convenient. Still it requires a good deal of time, and, in the case of a large instrument, of hard work; and if there are sensible irregularities upon the pivots of the instrument it is a very troublesome operation to ascertain and apply the necessary corrections.

The second and third methods are still more laborious: the second gives the level error corresponding to but one single position of the telescope, i. e., with the telescope pointing downward, and is therefore liable to a constant error depending upon any malformation of the pivots which affects the instru ment in this particular position: the third method can be used only when the air is perfectly still.

The method I have to propose, allows the determination of this error without any further labor than two readings of a microscope, in any position of the telescope, and without that uncomfortable climbing which is involved in the use of the striding level or nadir observations.

The annexed diagram illustrates the arrangement of the apparatus, in which, however, no regard is paid to the relative proportion of parts; the prism and mercurial horizon being grossly exaggerated in size for the sake of distinctness.

The axis of the instrument is to be fitted up as a collimator in the same manner already practised by Challis, Airy and others. In place of cross-wires, however, the extremity A should be provided with a plate of thin glass having a minute dot or circle engraved upon it, the plate being adjustable so that this dot can be brought into the geometrical axis of revolution and into the focus of the small object-glass which is situated in the other pivot, O. A reading microscope, M, is attached to the pier and provided with an ordinary collimating