i88o.] 
On Water and Air. 
49 
ON WATER AND AIR.* 
By John Tyndall, D.C.L., LL.D., F.R.S., 
Professor of Natural Philosophy at the Royal Institution 
of Great Britain. 
Lecture I. 
IfpIFTY-TWO years ago, commencing on a day in the 
frf year 1827, Mr. Faraday gave the first course of 
juvenile lectures in this place, and the leaures have 
been continued every Christmas without interruption from 
that time to the present. For years before his death, when 
he had given up all other engagements, it was his habit to 
leaure every year to boys and girls at Christmas, for he 
thought it a most important thing that they should not grow 
up in the midst of this wonderful system of Nature in which 
we dwell without knowing something about it. There can- 
not I think, be a doubt that a great deal of the interest 
that is now taken in the scientific education of the young 
may be traced back to those juvenile leaures which Faraday 
delivered in this room. 
A. knowledge of the phenomena and laws ot .Nature is 
sometimes called “ natural knowledge.” The Royal Society, 
for instance, which was founded 220 years ago, announced 
its obiea to be “ the improvement of natural knowledge 
and I trust that we who are here assembled together in the 
Royal Institution, which was founded 80 years ago, will, for 
the next fortnight, work cheerfully together in the great 
field in which natural knowledge is to be gained. 
I have chosen for this course of leaures two of our most 
familiar substances— Water and Air. Water is a very com- 
mon article of diet. If you take a man weighing n stone, 
and weigh the muscles of that man separately from the 
bones, they will weigh about 64 pounds ; but if you dried 
those muscles, so as to convert them into a dry mass, they 
* Being a Course of Six Lectures adapted to a Juvenile Auditory, delivered 
at the Royal Institution of Great Britain, Christmas, 1879. Specially re- 
ported for “ The Journal of Science.’ 5 
VOL. II. (THIRD SERIES). E 
