MEAN SCOTTISH METEOROLOGY. 277 



themselves for every day in the month, as given in the older Tables V. and VI. , — I have 

 called these special figures of the new Tables XXVII. and XXVIII. — borrowing the phrase 

 from the powerfully written geological volume of that too short-lived man of rare genius, 

 the late Campbell of Islay, — Tables of " Frost and Fire." 



Table XXVII. , representing "Frost," or the greatest depression of temperature below 

 32°, observed on one night in the month, but at the mean of all the stations actually 

 named, under the corresponding date in the previous bulky Table XXVIa. 



And Table XXVIIL, representing " Fire," meaning of course the Solar fire with its 

 marvellous powers of heat radiation on its one maximum day in the month, but at the 

 mean of all the stations particularised for that date, as before, in Table XVIa. 



For the " Frost " return alone, these numbers of Table XXVII. are not very different 

 from those given already by the exposed Black-bulbs as their mean of every night ; or say 

 12°'5 lower ; or by the mean of every night of the shaded Thermometers, viz. 17°'3 lower, 

 than them. 



But for the " Fire " returns, the numbers of Table XXVIIL are greater than what 

 were deduced from the exposed Black-bulbs on the mean of every day by 20° *8 ; and from 

 the mean of the shaded Thermometers by no less than 39° - ; and this on the mean of all 

 the months of the average annual cycle. 



What is still more important too, as indicating the Solar origination of the excess, is, 

 that this last extra quantity, though attaining only 34 o, at mid-winter, rises to 80°*6 at 

 midsummer, and cannot be neglected by open-air workers, either as a natural phenomenon, 

 or a practical fact testifying to the existence of an orb in the heavens above us by day, 

 of far more intense powers of heat-radiation, than there may be of cold radiation at night. 

 Entirely vitiating therefore the assumed official method of taking certain means, by 

 attending to the two extremes only. For if we take the mean of the hottest " fire," and 

 coldest "frost" month in a year, viz. +80° '6 and — 18°'0, their mean comes out 31°'3 ; 

 but if of all the 12 months of each kind, viz. + 59'5 and — 9"4, that result is only 25 o, ; 

 i.e. 25° above 32 o = 57°'0 F.; just as the first result means 31°'3 + 32 o, = 63°-3 F. 



Even too does this intense Solar radiation in summer on exposed surfaces, make 

 itself felt, though rarely, in some interiors. For on entering the dark, yet ventilated iron 

 Dome of the Royal Observatory, Edinburgh, on the 17th of last July, and finding its 

 atmosphere most unduly warm, I traced that effect to the invisible heat-rays coming 

 through the solid iron plates at, and about, where the Sun was shining on the outside ; 

 and with such force, as to produce a feeling on one's face (though in darkness, and at a 

 distance of several feet from the hot iron), like the sun-burning of an African desert. 



While on testing further the actual contact effect, by placing my hand on the middle 

 of the back of each curved plate, above the cylindrical part of the Dome, — I found that 

 there were four of those plates, extending over 90° of azimuth, so hot, that I could not 

 keep my hand's palm on them in close contact for more than a few seconds at a time. 

 The plates next on the right and left of that horizontal subtense being only agreeably 

 warm ; and beyond that range rather cool than otherwise. 



VOL. XXXV. PART 3. 3 A 



