the accuracy or applicability of his tables. He has not only abstained from publishing the mean results of the dry-bulb observations, but also those of the wet-bulb; and contents himself with publishing certain deductions alone, and an estimated mean temperature, a compound result of altered dry bulb and altered self-registering thermometric means—and this result deduced on a principle which every one who examines it must condemn. This practice, in a public observatory, whose observations are made and published at the public expense, is strongly to be condemned. Whatever corrected (?) mean results, or deductions from these, are published, the strict means of the whole of each series of original observations, freed merely from instrumental errors, ought to be given in full at the same time, in order that others, who consider the tables used for their correction to be erroneous, or who, though they admit the principle of the correction, may consider a five years' period of time far too short to give trustworthy means, or who deny that corrections proper for Six's instrument are at all needed for those constructed on Rutherford's, or Negretti's, or Phillip's principle, or who may wish to verify the accuracy of the corrections applied, may have it in their power to examine the subjects for themselves. Besides, the calculator may have blundered his calculations; he may have added a correction when he ought to have deducted it, and the estimated results, as published, may differ widely from the truth.

But it is not only the Greenwich observations which are altered in this manner. Mr Glaisher, from his position as Secretary to the Meteorological Society of England, alters in the same manner the results from all the fifty-five Meteorological Stations in England; and as he similarly withholds the strict means of the different series of observations made with the dry and wet bulb thermometers, he prevents all inquiry as to the correctness of the alterations which he makes.

In order, then, to prove that the mean temperature as deduced by taking the strict mean of the maximum and minimum readings of the self-registering thermometers, is far nearer the true mean than when altered by Glaisher's Tables, reference will be made to the Scottish series of observations, which are

made with trustworthy instruments; and which, from their very number, ensure an accurate mean result, much more truly than if they were the limited observations made at one station. But in Scotland we have, in addition, a series of observations carried on at Makerstoun, by our late venerable and honoured President, Sir Thomas M. Brisbane, with a care and accuracy which nothing can surpass. Reference will therefore also be made to the Makerstoun observations, for the years 1857 and 1858, to illustrate and prove the same point.

The following table gives the mean readings of the maximum and minimum self-registering thermometers, and alongside of these, the mean of the morning and evening 9 o'clock readings of the dry-bulb thermometer at Makerstoun, for the several months of the years 1857 and 1858:

By this table it will be seen, that at Makerstoun, in the south of Scotland, the mean temperature, as given by the 9 o'clock morning and evening readings of the dry-bulb thermometer, is so very close on that of the self-registering mean, that the difference might almost result from the mode of taking the readings. The tenths of a degree are all estimated by the eye, and according to the level at which the in

strument is presented to the eye, there may easily be differences of several tenths of a degree. The slight differences, however, between the means of the two kinds of instruments may have been caused by the Sunday readings having been included in the readings of the self-registering thermometers, whereas no Sunday observations are taken with the dry-bulb thermometer.

Let us, however, suppose for a moment, that the Greenwich Table of Corrections,* for the dry-bulb reading at 9 o'clock, applied to Makerstoun. On the mean of the year, they would add six-tenths of a degree to the mean of the dry-bulb readings, and thus bring the mean of the dry-bulb for the year 1857 to 48°1, and that of 1858 to 46°6. To procure a mean result, however, for these years we may, for the sake of illustration, unite the means, and divide by two, when we get, as the mean result of the two years, the mean temperature of the dry-bulb corrected by the Greenwich Tables, as 47°-3; while the mean of the self-registering thermometers as observed, and without any correction whatever, is within one-tenth of a degree of the very same-viz., 47°.2. This fact of itself clearly proves, that the mean temperature which is the strict mean of the selfregistering thermometers (when these are of proper construction) is the true mean, and requires no correction whatever.

This fact is still better and more satisfactorily demonstrated by the Makerstoun observations for 1844, the last of the Makerstoun Meteorological Reports published by the Royal Society, which contains SUMMARY Tables of the hourly readings of the common thermometer. In the annexed table, the Sunday readings of the self-registering thermometer are excluded, in order to render the results of dry-bulb and selfregistering thermometers thoroughly comparable,-no readings of the dry-bulb being taken on Sunday.

* Two tables for diurnal range have been drawn up in Scotland-viz., for Leith and for Culloden. The data on which these are founded are too imperfect to render them trustworthy. They however demonstrate, that the horary (miscalled diurnal) range of temperature is very much less in Scotland than at Greenwich.

By this table it is seen that the mean annual temperature, as taken by the hourly readings of the dry-bulb thermometer, was 44°.93, while by the self-registering thermometer it was 45° Fahr., a correspondence so close that it is scarcely possible to get a nearer approximation. Here, then, we find that hourly readings of the dry-bulb thermometer give an annual mean temperature within one-tenth of a degree of the strict mean of self-registering thermometric observations; and as we all know the care and accuracy with which the Makerstoun observations are made, even if this fact stood alone, it would prove the point contended for-viz., that, in so far as yet appears, the strict mean of the self-registering thermometers, when these are of proper construction, give the true mean temperature. It may be remembered, that all the tables of correction which different meteorologists in this country and on the continent have published, for the purpose of correcting the mean values of the self-registering thermometers, were drawn up from observations made with that untrustworthy instrument, Six's self-registering thermometer-an instrument so notoriously untrustworthy, that it would not now be received into any observatory in this country.

NEW SERIES.-VOL. XI. NO. II.-APRIL 1860.

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These results, then, appear to demonstrate, in the most satisfactory manner, that in Scotland the self-registering thermometers, if of proper construction, give the true mean temperature and require no correction whatever. This conclusion is rendered still more certain by taking the mean of all the observations made in Scotland with the two sets of instruments during the years 1857 and 1858.

This table, then, affords an additional demonstration of the fact that, in Scotland at all events, the mean of the selfregistering thermometers gives the true mean temperature, and requires no correction whatever for any supposed monthly variation. It also shows, what the Leith and Makerstoun observations had previously demonstrated, that the 9 o'clock morning and evening readings of the common thermometer give a very close approximation to that mean; so close, indeed, that for all ordinary purposes their mean results might be used wherever the means of the self-registering thermometers were unattainable.

But, as before remarked, Mr Glaisher would allow no result to be published as observed, but would apply to all results some fancied correction. Having, therefore, made his correc