112 



T. MIZUX0. 



Fig. I. 



§ 3. The face of a flat wooden block of convenient size, say, 

 10 cm. on a side, was pasted over with very fine tinfoil, as described 

 in my former paper. 



Then came cutting lines into the tinfoil, to which particular 

 attention was given. Along the edge of a bamboo ruler a sharp 

 knife, held always inclined away from the ruler, was drawn lightly 

 across the surface of the tinfoil. In this way, many 

 fine parallel slits were cut in the tinfoil, so as to 

 make one continuous, regular, zigzag line, as shown in 

 Fig. I. 



A few of the gratings, thus carefully prepared, 

 were found to be sensitive. But experience has taught 

 me that success in preparing good detectors depends, 

 to a large extent, upon the nature of the wood block 

 on which the tinfoil is pasted in the first place and 

 next upon the degree of adhesion of the foil to the wood. A soft 

 wood is preferable to a hard one, and the paste used should not be 

 thick enough to make the foil adhere too firmly. 



§ 4. The majority of the slits of the sensitive gratings, when 

 examined under ;> microscope, presented such an appearance as that 

 shown in Fig. II. A B and C D represent two 

 strips of foil with the very narrow slit or gap ab 

 between them that has been formed by the knife. 

 The shaded portion indicates the slope of the tinfoil 

 found at one edge of each strip. 



For the sake of clearness, there is shown in 

 Fig. III., an end view, that is, a section of the two 

 strips perpendicular to their lengths. The shaded 

 portions indicate the tinfoil strips, A B and C D in 

 Fig. II., of which the edge of one strip, C D, extends some 



II. 



C 



