72 LABORATORY LESSONS IN GENERAL SCIENCE 



4. At the end of each semester, and at the end of the 

 school year, note the seasonal changes as shown in the 

 twelve o'clock averages. Seek to account for them. 



SOLAR HEATING 



1. Set the insolation apparatus * in a south window and 

 so adjust it that a beam of sunlight, passing through the 

 box and falling upon a sheet of paper lying horizontal, 

 shows the narrowest outlines of the box walls. 



2. Measure the area of the paper covered by the sun- 

 beam that gets through the box, and tabulate the results 2 

 called for in the form below : 



1 A "breakfast food" carton with both ends removed serves the purpose 

 well. To a block of wood sufficiently large and heavy to serve as a base, 

 tack a strip of wood for an upright ; to this attach the carton in such a 

 manner that it turns readily in a vertical plane. Turn the whole apparatus 

 sidewise, and the carton up and down, to get the narrowest possible shadow 

 of the walls of the carton. 



2 See footnote of lesson on Temperature Records. 



3 With a protractor measure the angle between the edge of the upright 

 when vertical and the upper edge of the box as it stands properly ad- 

 justed. 



