[April, 
234 On Space of Four Dimensions. 
I have already in the above-cited treatise discussed some 
physical phenomena, which must be possible for such four- 
dimensional beings, provided that under certain circum- 
stances they are enabled to produce effects in the real 
material world that would be visible, i.e ., conceivable to us 
three-dimensional beings. As one of these effects, I discussed 
at some length the knotting of a single endless cord. If a 
single cord has its ends tied together and sealed, an intelli- 
gent being, having the power voluntarily to produce on this 
cord four-dimensional bendings and movements, must be 
able, without loosening the seal, to tie one or more knots in 
this endless cord. 
Now, this experiment has been successfully made within the 
space of a few minutes in Leipzig, on the 17th of December, 
1877, at 11 o’clock a.m., in the presence of Mr. Henry Slade, 
the American. The accompanying plate shows the strong 
cord with the four knots* in it, as well as the position of my 
hands, to which Mr. Slade’s left hand and that of another 
gentleman were joined. While the seal always remained in 
our sight on the table, the unknotted cord was firmly pressed 
by my two thumbs against the table’s surface, and the remain- 
der of the cord hung down in my lap. I had desired the tying 
of only one knot, yet the four knots — minutely represented 
on the drawing — were formed, after a few minutes, in the 
cord. 
The hempen cord had a thickness of about 1 millim. ; it 
was strong and new, having been bought by myself. Its 
single length, before the tying of the knots, was about 
148 centimetres ; the length therefore of the doubled string, 
the ends having been joined, about 74 centims. The ends 
were tied together in an ordinary knot, and then — protruding 
from the knot by about 1*5 centims. — were laid on a piece of 
paper and sealed to the same with ordinary sealing-wax, so 
that the knot just remained visible at the border of the seal. 
The paper round the seal was then cut off, as shown in the 
illustration. 
The above-described sealing of two such strings, with my 
own seal, was effected by myself in my apartments, on the 
evening of December 16th, 1877, at 9 o’clock, under the 
eyes of several of my friends and colleagues, and not in the 
presence of Mr. Slade. Two other strings of the same 
quality and dimensions were sealed by Wilhelm Weber with 
his seal, and in his own rooms, on the morning of the 17th 
* In the enlarged drawings the knots have been represented by mistake 
symmetrical ; they were tied on one side, in accordance with the small figure 
of the cord* 
