ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 289 



from all kinds of infective germs, and therefore epidemic diseases are 

 unknown at sea, except in so far as they arise from the material, pro- 

 visions, or water of the ship, or have been brought on board by crew or 

 passengers. Much of the benefit which would otherwise be derived 

 from a sea voyage is often counteracted by the small space and diffi- 

 culties of ventilation of sleeping berths and cabins. The temperature 

 of the tropics has a bad effect upon the crew and passengers of ships 

 from colder climates, and loss of weight results; but, in general, the 

 weight and strength of passengers are increased by voyaging in a fair 

 climate. Much depends, of course, upon the accommodation and diet, 

 as well as upon the atmospheric conditions. 



THE IMPROVEMENT OF CLIMATE WITH SLIGHT ELEVATION. 



From a certain number of experiments and from a review of observa- 

 tions taken by meteorologists of differences between temperature and 

 humidity at different heights above the ground, the present writer 

 came to the following conclusions, 1 shortly stated: 



The mean temperature at a height of about 100 feet above the 

 ground does not differ sensibly from the mean temperature at 5 feet, 

 but seems to be slightly in excess. 



The means of daily maxima at heights of 09 and 128 feet fall short 

 of the mean maxima at 10 feet, and still more of the maxima at 4 feet. 

 The means of daily minima at the greater heights exceed the mean 

 minima at the smaller heights. 



There is a certain altitude, apparently about 150 feet above the 

 ground, at which, while the mean temperature is equal to that at 4 feet, 

 the maxima are lower and the minima higher than at any lower point. 



On an average of nineteen months, the mean of maxima was about 

 1.5° F. lower at 128 feet 10 inches than at 10 feet, and the mean of 

 minima about 0.55° higher. 



In cyclones the higher, and in anticyclones the lower, points gen- 

 erally have the lowest mean temperature. 



The mean night temperature is always highest at the higher points, 

 and the mean day temperature always lowest. 



About sunset in clear or foggy weather, when calm, temperature falls 

 much faster near the ground than at some height above it. 



Equality of lower and upper temperature seems to occur about two 

 hours before sunset and after sunrise, but varies with the season. 



In clear weather and low fogs, between sunset and sunrise, tempera- 

 ture is always, or nearly always, higher at heights varying from 50 to 

 300 feet above the ground than at heights from 2 to 22 feet. 



In bad weather the higher points are coldest by day and night. In 

 foggy weather, especially with ground or radiation fogs, temperature 

 is very much the lowest near the ground, and within the fog much 

 lower than above it. 



1 Trans. Sanit. Inst, of Great Britain. 



sm 95 19 



