28 SCHOOL SCIENCE AND MATHEMATICS

out prejudice and not opposed merely because they fail to fol-low traditional patterns. It seems likely that these changeswill develop along two lines to meet two different needs. Onecourse will be informational in character to acquaint the stu-dent with the results of scientific progress and will be designedchiefly for students who are not likely to go on to college. Theother will be designed for those who need a thorough ground-ing in scientific methods and principles. To these ends new textsare likely to be demanded, texts which will combine with theattractiveness and appeal of our popular scientific magazinesthe basic principles and training in scientific method of thestandard courses. They must present the subject matter witha wealth of illustrative material of all sorts and from a greatvariety of sources; effective and numerous demonstrations,motion pictures, current literature, and especially real studentexperimentation, self motivated and as far as possible, selfdirected as all real experimentation is.

ARE YOU CROSS AT CROSS-HAIRS?BY H. LYNN BLOXOM

High School, Fort Dodge, Iowa

Occasionally in the laboratory it is desired to improvise cross-hairs in atelescope not already equipped with them, or to make a hasty repair inorder to complete some urgent readings.Seldom is the ordinary laboratory stocked in a way to make this seem-

ingly delicate operation a desirable undertaking. Yet one may speedilymake a substitution that will pass�on first inspection�for the work of anequipped artisan, with very common materials.To do this, a drop of glue (Le Page’s, for instance) is allowed to stiffen

slightly, then the point of a needle is touched to the glue. A small beadadheres and this is touched to the edge of the circle that defines the fieldin the focal plane of the telescope lens. As the needle is drawn away, a thinthread is formed which hardens by evaporation. By one bold, deliberatemovement this thread may be stretched across the field, and attached tothe opposite edge by touching the needle to the metal. The needle shouldbe continued in the same direction as it is drawn away. Another threaddrawn at right angles completes the job.

It is necessary to have glue of the right consistency. A little experi-mentation and practice will show the way. Threads of glue are fragile whendry and yielding when moist, so it is necessary to assemble the telescopewith care. Otherwise, the hairs may be blown away even by collapsing thetelescope.

Filaments of other dissolved materials may be formed by similar tech-nic, with varying difficulty, and the results may in some cases be generallybetter and more lasting. Rubber cement gives larger threads which aresometimes desired, but they show a tendency to collect dust.