94 PROFESSOR PIAZZI SMYTH ON 
utterly rarefied gas which they contain, offers immense facilities to the electricity 
for dealing with it, so that a moderate size of galvanic battery, and a very little 
coil or sparking apparatus is all the observer needs to produce whatever light 
and heat he requires; while a single small box with a dozen or two of thin 
glass vacuum tubes, each charged with a residuum of some particular gas, 
will enable him to inquire at any moment that he pleases, into the physical 
constitution of what makes up near half the universe. And this, too, without 
having to go through any chemical processes for procuring each gas whenever 
he wants it, in its extremest purity, and utter deadliness too, it may be. 
The heroic maker of the tubes ran that danger, and the subsequent fortunate 
possessor of them when made and hermetically sealed, has only to observe the 
spectra which the gaseous traces give out from the depths of their transparent 
prison-house, according to their /ubels, if duly attested and warranted by the 
maker, when the spark is passed through them. 
But what security, do you ask, can a mere label, though war ae by any 
maker, or even your own observed spectrum for that matter, give as to the reality 
and purity of the particular element of chemical matter supposed to be under 
examination? and do these tubes last? and do the gases in them never weaken, 
or change, or Jeak out, you wish to know? Well, all that is really very 
important, both to be inquired into and to be published upon ; and it is, in fact, 
precisely what I have been looking into practically for a considerable length 
of time past; with great hopes too at last of helping this mode of research 
to become, if not easier and more elegant than it has already been made by 
others, yet safer, truer, and more powerful than ever. 
The beginning of these latter-day attempts of mine was made in this way:— 
Twenty vacuum tubes of different gases and one or two volatilizable liquids and 
solids, such as alcohol, iodine and sulphur, were procured in duplicate from the 
late M. GEISSLER, in the form finally arranged with a capillary-central tube by 
the late Professor PLucker of Bonn. But when their spectra were found by 
me, generally faint, vague, and uncertain, a new arrangement and principle of 
viewing was invented, and twenty other pairs were procured on that different 
arrangement from M. SALLERON in Paris. That new arrangement was founded 
on and constructed agreeably with the end-on principle of viewing, which I had 
the honour of setting forth before the Royal Scottish Society of Arts, in February 
1879, but which turns out to have been invented by Dr Von MonckHoveN 
of Gand, in Belgium, several years earlier. Since then, a slight, but still further 
improvement has been made in my tubes, by giving them longer internal polar 
wires, to assist the electricity in traversing the necessarily large. bulbs where its 
light is not wanted, and then throw itself with all its energy and along with any 
molecules of the gas it has caught hold of, into the capillary tube, and hurry 
along that with lightning like speed, and light as well. 
