A very singular circumstance was noticed also as to the effects of ozone on the different orders of animals. The above-mentioned effects, and others which accompanied them, the description of which would be out of place in these pages, were developed more freely in carnivorous than in herbivorous animals. Rats, for example, were much more easily influenced by ozone than rabbits were. The results of Dr. Richardson’s experiments prepare us to hear that ozone-periods, though characterized by the absence of certain diseases, bring with them their own forms of disease. Apoplexy, epilepsy, and other similar diseases seem peculiarly associated with the ozone-periods, insomuch that eighty per cent. of the deaths occurring from them take place on days when ozone is present in the air in larger quantities than usual. Catarrh, influenza, and affections of the bronchial tubes, also affect the ozone-periods. We see, then, that we have much yet to learn respecting ozone before we can pronounce definitively whether it is more to be welcomed or dreaded. We must wait until the researches which are in progress have been carried out to their conclusion, and perhaps even then further modes of inquiry will have to be pursued before we can form a definite opinion. _DEW._ There are few phenomena of common occurrence which have proved more perplexing to philosophers than those which attend the deposition of dew. Every one is familiar with these phenomena, and in very early times observant men had noticed them; yet it is but quite recently that the true theory of dew has been put forward and established. This theory affords a striking evidence of the value of careful and systematic observation applied even to the simplest phenomena of nature. It was observed, in very early times, that dew is only formed on clear nights, when, therefore, the stars are shining. It was natural, perhaps, though hardly philosophical, to conclude that dew is directly shed down upon the earth from the stars; accordingly, we find the reference of dew to stellar influences among the earliest theories propounded in explanation of the phenomenon. A theory somewhat less fanciful, but still depending on supposed stellar influences, was shortly put forward. It was observed that dew is only formed when the atmosphere is at a low temperature; or, more correctly, when the air is at a much lower temperature than has prevailed during the daytime. Combining this peculiarity with the former ancient philosophers reasoned in the following manner: Cold generates dew, and dew appears only when the skies are clear—that is, when the stars are shining; hence it follows that the stars generate cold, and thus lead indirectly to the formation of dew. Hence arose the singular theory, that as the sun pours down heat upon the earth, so the stars (and also the moon and planets) pour down cold.