INFLUENCE OF WEATHER ON ACIDS IN RAINFALL, 91 



Setting up the Collecting Ajjparatus. 



The stand should be placed in a suitable position and the spikes provided 

 for the purpose driven firmly into the ground through the holes in the base 

 of the stand. This method of fixing will serve in most cases, but in localities 

 where wind-storms of extreme violence are not unusual it will be advisable 

 to secure the stand by screwing it down to pegs of wood which have been 

 driven into the earth. The pegs should be about 2 inches by 2 inches in section 

 and at least 12 inches long, and sharpened at the end. The accompanying 

 diagrams show the method of setting up the apparatus and the two methods 

 of securing it. 



2. Sample Bottles. 



These are small glass-stoppered bottles which have been carefully washed 

 out with purest distilled water, and then allow to drain. They should not 

 be unstoppered until samples of rain-water are about to be placed in them, 

 and then the stopper should be replaced as soon as possible. They are con- 

 tained in specially designed cardboard boxes lined with corrugated strawboard, 

 in which they may be sent through the post office, either singly or in batches, 

 without danger of breakage. To each bottle has been attached a blank label. 

 Regular supplies of sample bottles will be forwarded as required. 



3. Glass Wool. 



A plug of this filtering medium should be placed at the apex of the col- 

 lecting funnel and should be renewed as often as it becomes soiled through 

 exposure. 



4. Bottle Brush. 



This brush is intended for cleaning the funnel and receiving bottle, and must 

 not on any account be used for other purposes. It should be hung in a con- 

 venient place and be kept free from dust and other substances which would 

 contaminate the collecting apparatus. 



5. Stationery and Sundries. 



(a) Printed forms for recording weather conditions on rainy days ; 

 {&) 1 dozen envelopes; 



(c) 25 addressed parcel tags for returning samples ; 



[d) Wrapping cord. 



GENERAL INSTBUCTIONS. 



Observers should note that it is of prime importance to guard against the 

 introduction of impurities into the rain-water. The Committee wishes to 

 receive the water as nearly as possible in the condition in which it falls to 

 earth. Contamination is more likely to occur before, or after, a fall than while 

 the rain is actually falling. Dust and smoke particles, grass-seeds, insects, 

 bird-droppings and the like, are likely to foul the funnel and receiver during 

 dry spells, and if these are not completely removed before the rain falls the 

 results of the chemical examination will be misleading. Much may be done 

 in minimising this source of error by selecting a suitable position for the 

 collecting apparatus. 



The Position of the Collecting Apparatus. 



In choosing a position for the collecting apparatus avoid proximity to 

 buildings, trees, and roads. The rain should be free to fall into the funnel 

 from all points of the compass. The site should, if possible, be enclosed in 

 such a manner as to prevent access by domestic and other animals. An ideal 

 position would be at the centre of a large enclosed grass-plot. The apparatus 

 should not be very far removed from the official rain-gauge, as the measure- 

 ments made in the latter will be made use of in the research, no measurements 

 being made in the former. 



Preparing the Apparatus. 



Before placing the funnel and receiver in position they should be rinsed out 

 with rain-water, and allowed to drain for five minutes. Rain-water collected 

 during a very heavy downpour is suitable for this purpose, especially if the 



