METEOROLOGY AND CLIMATOLOGY. 
7 
Clouds should occasionally be photographed as a record. This should 
be done especially when a type of cloud comes to be recognised as a 
usual one, for while exceptional forms may prove interesting a record of 
the usual forms is certain to be valuable. In this connection a protest 
may be made against the horrible custom of some amateur and of many 
professional photographers of printing in clouds from some stock negative 
in their pictures of scenery. The cloud is an essential part of a picture, 
and it is better to leave an over-exposed sky of natural cloud than to 
insert a beautiful representation of a cloud-form which may be one never 
visible in the particular place or at the particular season. 
Mist , Fog and Haze .—Mist or fog at low levels will of course be recorded 
whenever observed, and its density and duration noted. A good way to 
define the density of thick fog is to measure the number of yards at which 
an object becomes indistinguishable, and the most convenient object for 
the purpose is a person. Light mists lie over water or marshes at 
certain hours in particular seasons, and their behaviour should always 
be observed. It often happens that the distant view from a height is 
obscured by a haze not due to moisture, and this appearance should be 
noticed with a view to discovering its cause. The smoke from forest or 
prairie fires in Canada sometimes produces so thick a haze as to put a 
stop to surveying operations for weeks at a time. Haze is often due to 
dust blown from deserts, or ejected from volcanoes, and sometimes to 
swarms of insects. 
Bain and Dew ,— The journals of most travellers fail to give a clear 
idea of the prevalence of rain during their journeys, and it is much 
to be desired that something more explicit than “a showery day” or 
“ fairly dry ” should be recorded. The hour* of commencement and 
cessation of rain during a march should be noted, and some indication 
given as to whether the rain fell heavily or lightly. In this way any 
tendency to a diurnal periodicity of rain would be detected, and some 
definite meaning would be given to the terms rainy season and dry 
season. If rain occurs during the night it should also be recorded, and 
the amount of night rains should always be measured by means of a 
rain-gauge in the manner to be described later. 
The general condition of a country with regard to rain may often be 
judged from the appearance of vegetation or the marks of former levels 
of high-water in lakes or rivers. Thus on mountain slopes or the sides 
