602 
Notes. 
in the green tint of the peas. This practically disposed of the only 
anxiety which Professor Dewar felt as to the success ot the experiment, 
and expressed to me on July 25 : — 
‘ My own impression is that unless the sudden vacuum caused by 
the liquid hydrogen cooling has produced physical rupture of the 
seeds, they will germinate as usual. If they survive this awful strain, 
then I believe no increase of the time of cooling could produce 
any effect other than results from one hour’s exposure to such 
severe cold.’ 
The seeds were sown in a cool greenhouse, without heat, on July 27. 
On August 1 they had all germinated. In the case of the mustard, 
136 young plants were produced from 155 seeds ; the remainder had, 
however, germinated, but the seedlings had damped off. One of the 
packets of wheat, for some reason, germinated slightly more slowly 
than the rest. 
On August 5, I received a further packet of the seeds (the musk 
excepted) indiscriminately mixed. Professor Dewar wrote the same 
date: — ‘I have sent you seeds to-day which, if the treatment with 
cold can kill, ought to be dead. They have been immersed in liquid 
hydrogen for upwards of six hours, and no attempt was made to 
graduate the cooling. They were placed in the vacuum vessel into 
which the liquid hydrogen could drop from the apparatus, and had to 
take their chance. The seeds have been soaked in liquid hydrogen, 
and in this respect differ from the last that were cooled in a vacuum 
from being sealed in a glass tube.’ 
In this instance again the seeds did not show the smallest visible 
trace of the ordeal to which they had been subjected. They were 
sorted out and immediately sown, under the same conditions as before. 
By August 9 the seeds had all germinated without exception. I com- 
municated the result to Professor Dewar, and he informed me, 
August 15 : — ‘The temperature Fahrenheit to which the seeds were 
cooled was — 453° F. below melting ice.’ 
These are the details of the experiment. As it is not likely to be 
often repeated, I have thought it worth while to place them on record 
as precisely as possible. 
The first question that suggests itself, is what evidence we have for 
believing that the seeds have actually been brought to the almost 
inconceivable temperature with which they were surrounded. That 
they were so brought, Professor Dewar himself has not a shadow of 
