118 



KNOWLEDGE 



[May 1, 1894. 



THE PHYSIOLOaiCAL EFFECTS OF CITY ANT) 

 SEASIDE AIR. 



To the Editor of Knowledge. 



Sir, — In your very valuable article in the March number 

 of Knowledge on " Sewer Gas and Zymotic Disease," you 

 refer to the mysterious difference in the physiological 

 effects of city and seaside or mountain air. I venture to 

 think that this diiference is for the main part non-existent, 

 and that the effects which are attributed to it spring 

 mainly from other causes. Leaving out of sight the 

 changes in the mode of life, and comparative freedom from 

 care and worry, to which a great deal of the good influence 

 which those experience who leave the city to take a 

 holiday in the country is doubtless due, a great deal is also 

 to be attributed to changes in the physical surroundings 

 other than the quality of the atmosphere. In hot weather, 

 the most important of these, I believe, is the greater 

 practical coolness of the country, especially of mountains. 

 In a large town, the effect of the heat of the air is greatly 

 added to by the radiation of heat from bare roads, pave- 

 ments and walls, and not diminished to the same extent as 

 in the country by the movement of the air, which is 

 impeded by the rows of houses. 



It is during periods of excessive heat that the healthiness 

 of towns falls most below that of the open country, except 



Sir William Vernon Harcourt are nearly as bad. The 

 Czar's favourite Minister of Finance is also said to be in 

 the same plight. With such a visitation of cataract in the 

 eyes of public men, your readers may possibly be interested 

 in the following account of a simple method I have 

 discovered which enables a patient to see a cataract in his 

 own eye and note its growth and development, probably 

 better than any oculist can observe it for him. 



Cataract is said to be due to the gradual deposition of ; 

 oxalate of lime in the substance of the crystalline lens, at 

 first in small spots or streaks, sometimes in one part and 

 sometimes in another. The deposit gradually increases 

 until it penetrates the whole of the lens, causing blind- 

 ness. The remedy, then, is to remove the lens, and after 

 its removal the patient needs a substitute in [the form of 

 highly magnifying spectacles. 



All that is necessary to enable a patient to see his own 

 cataract for himself is a piece of card and a needle — a 

 visiting card will do very well. Pierce a clean round hole 

 near the middle of the card and hold the card up to the 

 light close to the eye, looking preferably in the direction 

 of a piece of blue sky. With the card near to the eye, 

 the patient will not see the small hole pierced by the 

 needle, but he will see a comparatively large faintly 

 Oluminated field with his cataract projected upon it. He 

 is, in fact, observing the shadow cast by his cataract on the 

 retina at the back of his eye. With a small puncture in 

 the card the shadow so thrown is comparatively sharp. 

 But with a normal eye an evenly illuminated field or clean 

 disc will be seen. The patient may thus map down his 

 own cataract, and settle for himself whether it is extending 

 and whether he will have an operation or not. None of 

 the oculists I have seen have known of the method, and 

 there may, consequently, be some advantage in making it 

 public. I enclose for your inspection drawings, which I 

 have made at intervals during the last three years, of a 

 cataract which is slowly developing in one of my eyes. If 

 you accept this communication please not to publish my 

 name, as it might be a disadvantage to me in my business 

 if it was thought that my sight was defective. 



Yours truly, 



J. S. 



in very large towns where there are dense smoke-laden 

 fogs. In cold weather, even when there are no such fogs, 

 the air of large towns is commonly so much more smoke- 

 laden and cloudy than that of the country as to shut out a 

 great deal of the light and warmth of the sun, and thus 

 gives rise to a lowering of vitality and spirits. 



Close observation for many years has convinced me that 

 these circumstances, and not any supposed difference in 

 the quality of the air, are the source of the benefit derived 

 from "a change into the country." 



I am, Sir, yours truly, 

 Tunbridge Wells. Edw. G. Gilbert, M.D. 



[Dr. Gilbert would have added to the interest of hia 

 letter if he had shown how he manages to distinguish 

 between the beneficial effects produced by the various con- 

 current circumstances alluded to as generally accompanying 

 the dose of fresh air. — A. C. Ranyard.] 



THE FACE OF THE SKY FOR MAY. 



By Herbert Sadler, F.R.A.S. 



SEVEEAL large groups of sunspots have of late 

 appeared on the solar surface. 

 Mercury is invisible during May. He is in 

 superior conjunction with the Sun on the 20th. 

 Venus is a morning star, rising on the 1st at 

 3h. 15m. A.M., with a southern declination of 2° 19', and 

 an apparent diameter of 22j", -j^'^ths of the disc being 

 illuminated, and her brightness being about equal to what 

 it was on January 25th. On the 16th she rises at 2h. 47m. 

 A.M., with a northern declination of 2° 34', and an apparent 

 diameter of 19j", -r^ths of the disc being illuminated, 

 and the apparent brightness of the planet being about 

 equal to what it was on February 1st. On the 31st she 

 rises at 2h. 21m. a.m., with a northern declination of 

 8° 37', and an apparent diameter of 17^", y^^^s of the 

 disc being illuminated, and her brightness being about 

 equal to what it was on February Brd. During the 

 month Venus pursues a direct path through Pisces to the 

 borders of Aries. 



Mars is, for the purposes of the amateur observer, 

 invisible ; and Jupiter and Neptune have left us for the 

 season. 



Saturn is an evening star, and is well situated for 

 observation. On the 1st he rises at 5h. 4m. p.m., with a 

 southern declination of 5° 24', and an apparent equatorial 

 diameter of 18-6" (the major axis of the ring system being 

 42-8" in diameter, and the minor 9"). On the 16th he 

 rises at 4h. Om. p.m., with a southern declination of 5° 5', 

 and an apparent equatorial diameter of 18-4" (the major 

 axis of the ring system being 42-3" in diameter, and the 

 minor 8'6"). On the 31st he rises at 2h. 58m. p.m., with 

 a southern declination of 4° 53', and an apparent 

 equatorial diameter of 18"0" (the major axis of the ring 

 system being 41-1" in diameter, and the minor 8'2"). 

 Titan is at his greatest eastern elongation on May 14th 

 and 31st, and lapetus at his greatest western on the 17th. 

 During the month Saturn describes a short retrograde 

 path in Virgo, but does not approach any naked-eye star. 



Uranus is an evening star, and but for his southern 

 declination would be well placed for observation. He is 

 in opposition to the Sun on the 3rd, at a distance from 

 the earth of about 1637j- millions of miles. He rises on 

 the 1st at 7h. 23m. p.m., with a southern declination of 

 15° 29', and an apparent diameter of 8-8''. On the 31st 

 he rises at 5h. 13m. p.m., with a southern declination of 

 15° 8'. During the month he describes a short retrograde 



