12 C. TIAZZI SMYTH ON 



them appeared by contrast of pitch-like darkness, though without preventing 

 a good sized star from shining forth ; — and the brightness of the clouds con- 

 tinually increased from the Zenith down towards the Southern direction, so far 

 as the neighbouring Calton Hill allowed one to look into that quarter. 



The affair was so unusual, that I immediately made my preparation for 

 going expressly to the top of the said Calton Hill, in order to look further down 

 South, and see what strange source of light there could be there, illuminating 

 the clouds so strongly ; — for the Almanac declared that there was no Moon in 

 the position at that time, nor would be for several hours. 



The ascent of the hill under such circumstances was rather tantalising ; — 

 for the first part of the way, by bringing one closer thereto, produces a higher 

 angle of obstruction for the summit, — and meanwhile the clouds overhead and 

 around, glowed with such an unnatural glare of light, as made me fear it could not 

 last long, and that I might be too late after all to see its origin in full force, and 

 behold whence it came. Tree tops of neighbouring gardens projected on some 

 of these clouds, showed their detail of twigs with almost daylight minuteness'; 

 and on coming into view of Nelson's Monument, though still a long way off, 

 there was not only the Time-Ball on its summit, but there were its staff and 

 cross-arms, each and every one clearly visible and even black and sharp against 

 one of these preter-naturally bright clouds. But on reaching the top of the hill, 

 and getting a view from thence right down to the Southern horizon, there was 

 nothing there in the heavens, or apparently anywhere else to account for the 

 strange scene up above. The effect so very strong up there, simply died away 

 from inanition in the distance towards the South. 



Baffled then and disappointed I entered the Royal Observatory enclosure 

 and watched the strange bright clouds overhead or nearly so, as they were 

 wafted about, but chiefly from East to West, for nearly a couple of hours. The 

 air was cold and dry. The clouds were of the massive, but irregular figure of 

 cumuli when seen at a high angle of altitude, and their light gave to spectro- 

 scopic examination nothing but the faintest continuous spectrum in the green 

 region. Not in the slightest degree therefore like Aurora, with its sharp citron 

 line ; but rather like the faintest trace of carbon-flame illumination. 



Gradually the disastrous and humbling idea grew in my mind,- — that this 

 wondrous phenomenon of luminous night clouds was nothing but their reflection 

 of the gas-lights of Edinburgh and Leith, Portobello and Granton ; and I tried 

 to dismiss the matter from my mind. But every subsequent night that showed 

 the usual rule of clouds dark against a starry sky, — though said clouds were 

 illuminated by just the same city gas-lights, — brought up the further and per- 

 haps more important question " why and how were clouds able to reflect such 

 abundant light on that one night of April 8 alone ?" 



Besides the postulate that the air must have been very clear, two other 



