228 Pub. Puget Sound Biol Sta. Vol. 2, No. 47 



and top. The trays are filled with moss of about the same degree of damp- 

 ness, and the wheel is kept in motion by a one horse-power electric motor. 



In connection with this drying apparatus some valuable experiments 

 were, undertaken to ascertain if humidity is a factor to be considered in 

 drying moss artificially.^ To this end an attempt was made to make the 

 atmosphere of the drying room similar to that which might be called a 

 good drying day, with special care as to the relation of temperature and 

 humidity. Artificial heat was furnished by a gas heater. The tempera- 

 ture was regulated by means of gas burner rings of different diameters, 

 three in all, controlled by stop cocks as in a gas range. Air was forced 

 through the heater by an electrically driven motor (I/2 H.P.) making 2700 

 revolutions per minute. The temperature maintained in the drying room 

 was made to conform to the percentage of relative humidity desired. In 

 any event, the temperature was not allowed to rise about 105° F., as a 

 higher temperature seemed to be deleterious to the moss. On days of low 

 humidity moisture was provided for by live steam, by a pan of water on 

 the heated pipe from the heater, or by passing intake air over water. 

 Wet and dry bulb thermometers were used to determine the condition of 

 the room air and outside air. 



For the first one or two hours of drying, depending on the moisture 

 content of the moss, the relative humidity was held between 50% and 60% 

 to avoid too rapid drying. When the sphagnum appeared to be about 

 half dry, the percentage of relative humidity was lowered, and the drying 

 was finished with a relative humidity of about 30%. If the moss was half 

 dried in the racks before being put in the wlieel the relative humidity was 

 at once lowered to about 30%. 



The wheel, when originally installed, made six revolutions per min- 

 ute. This was increased to eight revolutions per minute, increasing the 

 mean velocity of the outer trays from 188.5 feet (57.5 m.) per minute to 

 251 feet (76.5 m.) per minute, the mean velocity of the inner trays from 

 94 feet (27.7. m.) per minute to 125.6 feet (38.3 m.) per minute, with 

 beneficial results. 



The moss in the outer trays dries more rapidly than that in the inner 

 trays, furthermore, the moss at the edges of the outer trays exposed to a 

 larger volume of air, dries more rapidly than that at the edges exposed 

 to a smaller volume. It was found advisable not only to exchange the 

 inner trays with the outer ones during the process of drying, but also to 

 turn the trays half way round to get uniformity in drying. 



Sometimes it was necessary to run the wheel all night in order to 

 obtain sufficient moss, but in such cases the heater and blower were shut 

 oif at 10 P. M. It requires from 10 to 12 hours for all the moss on the 



» The writer is Indebted to Mrs. Austin R. Baldwin for tlie facts concerning these experiments. 



