382 
Proceedings of the Royal Society 
3. On a Case of Interlacing Surfaces. By Professor 
Crum Brown. 
The simplest form of the interlacing surfaces as spread upon a 
plane is illustrated in fig. 1. It will he seen that we have here 
Fig. 1. 
three sheets, differently shaded so as to distinguish them to the eye, 
hut otherwise quite similar. 
