62 



SCIENCE 



[N. S. Vol. XL VI. No. 1177 



marks from shade cloth, to any extent, but 

 lead pencil marks are more easily removed 

 than from paper. When a mistake is made 

 with ink that can not be erased, I find it 

 best to paste a bit of the shade cloth over the 

 error. This is not noticeable at the distance 

 of even the front row, in any ordinary lecture 

 room. 



For making lines, I find so called round- 

 writing pens (single pointed) better than a 

 ruling pen as it is hard to make lines broad 

 enough with the latter instrument. Round 

 writing pens may be obtained in different 

 widths, and they are inexpensive. The wider 

 pens are useful especially for making bold 

 strong lines to be seen in a lecture room of 

 some size. 



Most of my charts are made with water- 

 proof inks of the best grade. These are kept 

 in various dilutions in a series of one-ounce 

 bottles. Thus I keep about six dilutions of 

 black ink in as many bottles labelled one to 

 six, for use in neutral gray shading. A few 

 drops of black ink in an oiuice of water make 

 a dark shade. Several drops of this added 

 to an ounce of water in another hottle make 

 a weaker solution, and so on according to the 

 eye of the user. 



I dilute the colored inks usually by placing 

 a few drops of ink in an ounce of water, ac- 

 cording to the color desired. Many varieties 

 of color shade and tint may be obtained by 

 mixing colors in water and by adding a little 

 much-diluted black ink to a colored solution 

 in varying proportions. It is my practise to 

 dilute almost all of the ink used, to some 

 extent. Softer and more pleasing effects are 

 produced, and the ink goes farther.. It is also 

 more easily applied. 



For class use and for convenience in stor- 

 ing, I find it desirable to have charts 

 mounted. Two half-round pieces of one inch 

 diameter are glued together with the lower 

 end of the chart between their flat surfaces. 

 To make the binding still more seciire, nails 

 are also used. Light one-half-inch half- 

 round material is used for the top in the same 

 way. Straps for hanging, of strong braid 

 one half to three quarters of an inch wide 



and a foot or so long are fastened to the top 

 strips at suitable places. These also serve in 

 the usual way for tying the charts up when 

 rolled. It is particularly important that the 

 straps be attached strongly. 



Some readers of this article may not be 

 familiar with the possibilities of a pantograph 

 in copying small drawings enlarged on 

 charts. The best pantographs are expensive, 

 and the cheapest unsatisfactory. However, 

 I have found one costing about $5.00 of con- 

 siderable service. It enables one to get the 

 general outlines of the drawing, but tliese 

 must be corrected by free-hand work later. 



Neat labelling, that can be read in the rear 

 seats of the room in which the chart will be 

 used, is exceedingly important. It is my 

 practise both with charts and lantern slides 

 to avoid any details in either labelling or 

 drawing that can not be distinguished easily 

 in the more remote parts of any lecture room 

 in which the illustrations are to be used. 



It is distressingly common, especially when 

 lantern slides are employed, to find this rule 

 violated. Large sheets of typewritten ma- 

 terial are often crowded into a lantern slide 

 with the result that they can be read only 

 when very near the screen, if at all. In the 

 case of lantern slides, any details which can 

 not be distinguished easily in the slide will 

 also be too minute on the screen. In prepar- 

 ing charts it is a good practise to put letters 

 and drawing details of various sizes on a 

 blackboard which may be viewed from the 

 most distant seats in order to determine the 

 most practicable proportions. 



Labelling may be quickly and neatly done 

 with the aid of the so-called sign-painters' 

 rubber stamps. Sets may be bought in vari- 

 ous sizes and with both caps and small letters 

 as well as Arabic figures, etc. Inks of vari- 

 ous colors may be obtained for the stamping. 

 Quick-drying inks save time in the prepara- 

 tion of a chart. 



It is my experience that most and some- 

 times all the chart work described in this 

 article can be done by student service under 

 direction, especially if students who draw well 

 are available. 



