352 Winter Cover Washes 



likely hypothesis. Working on this it is at once apparent that to make 

 such a wash most efficient certain conditions must be fulfilled. These 

 are: 



(1) It must give a thick covering. 



(2) It must resist all external conditions causing lessening of 

 the coat when once on the tree. i.e. it should not flake when dry or 

 wash away when wetted by rain. 



(3) It should be applied as late in the spring as possible. 



(4) The materials should be reasonably cheap and easy to get. 



(5) It should be easily made. 



All the experiments hereafter described had to be done in the dead 

 season, beginning in the autumn of the year and ending in the late 

 spring of the following year when the buds had begun to burst. They 

 may be grouped more or less in a chronological order in order to retain 

 the sequence of ideas. 



Season 1912-13. 

 Laboratory experiments. 



Experiments were begun to find some mixture that was more 

 resistant to erosion than lime alone. In the first trials twigs were 

 dipped into the various mixtures and allowed to dry in the laboratory. 



It was found, however, that this method gave unsatisfactory results, 

 as the twigs themselves soon dried and contracted away from the 

 coating of material applied to them, so that the best wash under these 

 conditions soon began to flake. On the living twig this is not so. In 

 all subsequent laboratory experiments the washes were poured upon 

 ordinary 3x1 microscope slides and allowed to drain as they dried. 

 The smooth surface of the slide was an additional guarantee of good 

 sticking qualities. In practice, in the field, twigs are always slightly 

 rough so that any wash adhering well to glass slides should do so quite 

 as well when applied to a tree. Plain lime wash at the rate of 2 lbs. 

 to the gallon of water was used as control. It having been frequently 

 stated that the addition of waterglass or sodium silicate improved 

 the adhesiveness, this was first tried. All quantities are calculated 

 in pounds of material to pounds of water or in grains per c.c. 



The following (with the salt left out) recommended by Theobald 



Lime Waterglass Water 



20 1 lUU 



