58 
MAGAZINE OF SCIENCE AND ART. 
improved, of the contiguous sites, indeed, of the en¬ 
tire city. , ... 
2. By the reduced cost of constructing drams, 
and still more so of their repairs. 
3. By tho reduced cost of constructing roads and 
streets'throush the districts so improved, together 
•with the infinitely greater reduction in tho cost of 
keeping them in repair. 
4 . By ihe greatly decreased “ wear and tear” and 
“ risk” to vehicles of every description, as well as 
to draft animals, traversing those spots. 
5 . By a total abatement of those extensive losses 
to a large number of the proprietors of houses from 
the unsettled state of the levels hitherto, whence, in 
some instances, rows of houses arc seen (or were 
lately) literally buried below the street, with which 
at one time they were on a level, or, in other in¬ 
stances, perched like birds’ nests so high as to he all 
but inaccessible, if not quite so. 
Add to the above— , , , 
G. Store rents, rates for tho use of the fresh, as 
well as the salt water bathing places, for the use of 
the “Necropolis.” Reduction of insurance on firo- 
risks, from the greatly increased breadth of the 
streets, the absence of all laoes and alleys, and tho 
greatly increased supplies of water, as well as fi- 
cilities for applying it, to these add the value of the 
sewage as a substitute for guano, for which, it is 
now well known, it can readily he made, in every 
respect, a full equivalent, together with that of the 
offal from the Abbatoirs, both now lost to tho public, 
or, worse than lost, permitted to become a danger¬ 
ous and offensive nuisance. To the above I would 
only add (not that the subject is by any means ex¬ 
hausted) one observation, namely,—that the above 
direct and indirect gains, exclusive of numerous 
other obvious and highly important advantages, are 
not merely for the hour or the day, but in perpe¬ 
tuity, and 1 think I shall then be fully borne out in 
asserting, that while even the more immediate fruits 
of the proposed “reforms’’ would soon yield, at the 
most moderate computation, an ample requital for 
their cost, thero would then remain to the public an 
invaluable nett permanent gain. 
But, waiving all further consideration of the 
“direct” or “indirect” “gains” that would or 
might acorue from the proposed measures, granted 
that they would not produco any one of those large 
advantages, which wo know they would and must 
produoe, or indeed any advantage at all, save one, 
their sanitary results, (for the proof ot which 1 may 
refer to the accumulated experience of all ages, and 
this confirmed by modern science), and I then fall 
back upon what will not—nay, perhaps, I may be 
permitted to add, cannot bo denied, my original 
proposition, namely, " That no price, that we could 
afford to pay, could be too high in order to secure to 
our “ towns” and “ cities” the largost possible ex T 
tent of protection against those “ epidemics” which 
so frequently devastate the entire globe, as well as 
to the inhabitants generally, the largest attainable 
amount of longevity, and sound health.” 
IV. BLAND. 
ON A SUN-GAUGE, OR NEW 
ACTINOMETER. 
At the meeting of the Philosophical Society 
of New South Wales, held July 8, Sir W. 
Denison in the chair, the following paper 
was read by the Secretary, Dr. Smith, it 
being a contribution from Mr. W. S. Jevons. 
It is descriptive of the Actinometer, an in¬ 
strument invented by Mr. Jevons, for mea¬ 
suring the daily amount of sunshine. 
Scientific gentlemen present, competent to 
oiler an opinion on the subject, stated it to 
be a very valuable and ingenious invention. 
We have, therefore, prepared diagrams in 
order to give a more intelligible idea of its 
construction, and shall be glad to record the 
results obtained by its means, and give any 
other information in our power concerning 
it. We should also be glad to hear the 
opinion expressed upon it by the European 
scientific journals. 
It is allowed, I believe, that meteorologists are very 
imperfectly supplied with instruments for measuring 
the heating effect of the sun's rays. 
The Actinometer of Sir John ilerschel, though unex¬ 
ceptionable in principle, has been found very expensive 
and very difficult to use, and tile common black-bulb 
thermometer, which is generally employed, does not 
appear to give results of any direct value or compara¬ 
bility. But it scenes to mo that even if we did possess a 
convenient actinometer, fitted to determine, at any given 
place and moment, the intensity of the sun’s rays, that is 
to Say the rule of the sun’s heating power, thero is still a 
second instrument required in meteorology to measure 
the accumulated amount or total effect of the sun's rays 
during anv given length of time. 
In short, the sun’s heat should be collected as it were, 
and gauged, at every Meteorological Observatory, as it 
falls^upon the surface of the earth, day after day, and 
year after year, precisely in the manner that falling rain 
is collected lir tho rain-gauge, and its accumulated 
depth measured at the end of any convenient period. 
The instrument which will effect this, I should pro¬ 
pose to call a sun-gauge, from analogy with the rain- 
gauge, and this paper is intended to describe a method 
which, after proper elaboration, will, 1 hope, he found 
successful. The method in question is, in fact, merely 
an adaptation to a new use of the invention commonly 
known as Dr. Wollaston's Cryophorus , which I must 
first of all describe. 
Tho Cryophorus consists of a simple glass tube bent 
down and' terminated at each end by a round glass bulb. 
One of these bulbs is half-filled with pure water, and 
the whole instrument being then completely exhausted 
of air is hermetically sealed up. In this condition its- 
interior is occupied by nothing but water and watery 
vapour, the latter of a tension which depends on the 
temperature, and increases as the temperature rises. 
If, therefore, one bulb be warmer than the other, the 
vapour is of greater tension in tho former, and not being 
impeded by the presence of air, rapidly Hows into the 
colder bulb until equilibrium is attained _ This cannot 
happen, supposing there he liquid water in both bulbs, 
until the stream of vapour has conveyed away sufficient 
latent heat from tho warm bulb to reduce its tempera¬ 
ture to that of the colder. Tho singular effect is thus 
produced, which the Cryophorus is used in lecture- 
rooms to demonstrate, and from which it derives its ap¬ 
pellation, namely, tho apparent conveyance of cold from 
one bulb to tho’other. For the whole of the water 
being poured into cither of the bnlbs, and the opposite 
one being plunged into a freezing mixture, such a rapid 
evaporation and distillation is occasioned as soon to 
freeze the portion of water which yet remains in the 
bulb distinct from that to which the cold was applied. 
For our own purpose, it is only necessary to attend to 
one more consideration, viz., that the amount of latent 
heat contained in, or combined with aqueous vapour at 
anv given temperature, is not only invariable and de¬ 
terminate, but has actually been determined with great 
accuracy. Thus, at a temperature of 32 degrees,. water 
requires as large an amount of heat to convert it into 
vapour as would raise it in the liquid condition, if such 
a thing were possible, to the extent of 1092 degrees 
Fah. of temperature. Hence if we can determine the 
