The chairman expressed the interest he felt in this new pyrometer that had been brought before the meeting, and considered it an ingenious and efficient instrument. He remembered having had a conversation with the late Prof. Daniell on the subject of his pyrometer, and expressing a doubt of the nearness of the approximation in the results obtained from that instrument; in fact, such delicate manipulation was required in using it, that it was scarcely available except in the hands of the

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... himself. But Mr. Wilson's instrument was so extremely simple in the construction and practical application, that an accurate measure of the quantity of heat could be relied upon, with ordinary care in the employment of the instrument. It might be theoretically considered, that quantity of heat was a different point from intensity of heat,--as in the case of voltaic electricity the difference between quantity and intensity was known to be so strongly marked in the different effects produced; and this pyrometer, although measuring correctly the relative quantity of heat required to melt different bodies, might give far from a correct measure of the relative intensity of different fires. However, the same theoretical question applied of course to the ordinary mercurial thermometer, which was also the standard of measure in this pyrometer, and to all thermometers which measured the degree of heat by the relative expansion of any body by heat, whether mercury, iron, or air. --Proc..Mech. Eng" Birmingham. REMXaKs.--We do not doubt that for practical purposes, the very neat and simple process proposed by Mr. Wilson will be found very convenient and valuable; but for scientific accuracy, the loose eshblishment of equivalents will not answer, nor can the instrument be relied upon for delicate determinations, until the specific heat of platina at high temperatures shall have been determined; at present it is simply unknown. The pyrometer, invented by Prof. W. R. Johnson, used in the experiments on the explosions of steam boilers, by the committee of the Franklin Institute, and described in the .