March 7, 1889] 



NATURE 



443 



from Primrose Hill, and their names, are given in Table 

 I. The total number of times that each of the chosen 

 points was seen during the five months selected is also 

 given. 



It will be observed that during the 152 days which 

 make up the five months selected, Christ Church, Lan- 

 caster Gate, and St. Mary Abbot's Church, Kensington, 

 on the south-west line ; the Clock Tower, Houses of 

 Parliament, on the south line, and the Scotch Church, 

 Regent's Square ; and St. Paul's Cathedral, on the south- 

 east line, were never once seen. 



When it is known that on any ordinary fine day during 

 the late spring, summer, and early autumn, you can see 



right across London, on any one of the selected lines, it 

 will be easy to realize how thick the air over London is 

 during the winter. 

 I It may be noted that when you could see as far as St. 

 i John's Church, Hamp«tead, it would, as a rule, have been 

 possible to see much further, but since there was no point 

 beyond Hampstead which could be taken as a measuring 

 point, it was impossible to record the distance. 



(2) As regards the amount of artificial light used 



in various parts of London owing to the prevalence of 



I dark fog. The observations given below were made, 



[ with the assistance of various friends, during the winter 



I of 1887-88, and give the approximate result in hours. 



On nine days you could not see loo yards. On four days you c6aId.pot'si^^-5 yards. 



A few districts out of many others are given in 

 Table II. 



Tablk II. — Observations taken in London. 



The manner in which the observations (given in 

 Table II.) were made will be seen in detail from 



Table HI.,- which- was btpt by Mr. E. Liddell at the 

 College, Homerton, E. ' 



This table is given because Homerton' sunered more 

 from darkness than any other part of London, owing, it 

 cannot be doubted, to the large number of factories in the 

 neighbourhood. It will be seen later on in this paper 

 that Leeds suffered more from darkness than the other 

 provincial towns selected, and this was due probably to a 

 great e.xtent to the same cause. 



From Table II. it will be seen that January was the 

 worst month for dark fogs, the average for each of the 

 districts given being 27 hours of darkness per month. 



London is not much worse than our large provincial 

 towns in respect to dark fogs. Table IV. gives the results 

 of observations made in several towns. 



It will be seen from Table IV., that dark fog was 

 general in the tabulated towns during the month of 

 January. It is said that Manchester, of late years, has 

 been unusually free from dark fogs, owing to the fact that 

 a very large number of mills have been moved out, so as 

 to escape the heavy town rates, &c. The ordinary white 

 fog has also been reduced, probably through thousands 

 of acres of the wet morass lands on the west side of 

 Manchester having been well drained recently. This being 



» On thirty-six days this point could not be seen. 



