828 
Glow-worm. are winged; and Thunberg mentions one found in Ja 
—y~" with two vesicles on the extremity. The former descri 
their site as under the termination of the tail; and ob- 
serves, that the winged insects are extremely rare in 
England. 
The luminous substance, when extracted froma dead 
glow-worm, gives out no light, though the sacs, when 
cut from the living animals, shine several hours after 
separation; and, if put into water, they will emit 
light uninterruptedly for forty-eight hours. Whether 
they contain greater heat than the other parts of the 
animal, as a sufficient number have never yet been ac- 
cumulated to prove the fact by experiment, is not alto- 
gether free of doubt. John Templer, one of the ear- 
liest English observers of the nature of the glow-worm, 
says, “ If my senses fail me not, she emits a sensible 
heat in her clear shining.” Mr Macartney also thought, 
that, when shining brilliantly, the luminous rings com- 
municated the sensation of warmth to the hand; but, 
from remarking that the heat of the surrounding atmo- 
sphere, 69°, was not raised more than to-75° or 77°, on 
introducing a very sensible thermometer among several 
glow-worms, he concluded, that the actual difference 
of heat was insufficient to warn him of its presence. 
Sometimes, however, the luminous portion of the tail 
seemed to raise the thermometer more quickly than 
other parts of the body ; and on cutting it off several 
- animals, he found, that if the thermometer were im- 
mediately applied, it would rise one or two degrees ; 
but that no effect’: whatever was produced after’ these 
pee were dead, though they continued to give out 
ight. It ought to be kept in view, that many errone- 
ously believe insects are entirely destitute of heat, 
whereas its presence is sufficiently demonstrated by ac- 
cumulating a number together in a limited space. 
Besides the glow-worm properly so called, an insect 
wanting wings, there are several of the genus provided 
with them, and then generally denominated fire-flies. 
In the hot climates, thousands shoot across the eye, and 
sparkle in the woods and bushes during night, with 
the most beautiful and brilliant illumination. Some, 
resembling so many specks, are not larger than the 
common house-fly ; others are above half an inch long ; 
and several collected in a glass vessel, emit sufficient 
light for reading a book. All are of the coleopterous 
tribe: both sexes have wings, and the emanations pro- 
ceed from the last segments of the tail. 
Some general conclusions have been drawn regard- 
ing the nature of luminous animals, most of which ap- 
ply to the glow-worm: and first, that this property is 
not constant, but exists only at certain periods, and in 
particular states of the animal’s body. The site of its 
emanations, also, resides in a particular substance, com- 
pared to paste ; and the light is differently regulated 
while that substance is in the animal’s living body, or 
separated from it. In the former case; it is intermit- 
ting: it is commonly produced or augmented by a mus- 
cular effort, and is sometimes absolutely dependent on 
the will of the insect. In the latter case of separation, 
the luminous exhibition is usually permanent, until be- 
coming extinct, after which it may be restored directly 
by friction, concussion, and the application of warmth. 
No diminution of the: substance follows the exhibition 
of light, however long it may be protracted. It does 
not require the presence. of pure: air, nor is it extin- 
guished by other gases. The luminous appearance of 
living animals is not exhausted by long continuance, or 
frequent repetition, nor is it accumulated by exposure 
to natural ight. From these principles, it is inferred, 
that this property not being dependent on any foreign 
GLOW-W ORM. 
source, is inherent in a peculiarly organized animal G 
substance, and is regulated by the same laws which 
govern all the other functions of living beings. 
Many conjectures have been indulged aeere 
use of the light exhibited by luminous animals, 
have boldly Detiaied, that it is for no specific purpose ; 
others, more prudently, affirm, thatit is utterly unknown: 
while a third class, substituting opinion for i 
ment, at once decide that, in the glow-worm at "Teast, 
it is a wise provision of nature for promoting the con- 
course of the sexes. Undoubtedly this reason at first 
sight is plausible ; but it ought to have been previous- 
ly ascertained, that the male, while flying through the 
air, is sensible of the luminous emanations from the 
body of his grovelling mate. We know little of the’ 
different senses of insects; hearing seems altogether de- 
nied to certain species, and others are void of any ex- 
ternal organs of sight: but what is more extraordinary, 
neither the number nor size of the eyes apparently in- 
crease the acuteness of vision. It ought constantly to 
be preserved in remembrance, that the beautiful struc- 
tures of the bee are erected, and all its complicated 
operations performed, in ‘the dark ; but that other or- 
gans, and especially the antenna, are constantly re- 
sorted to by them as a guide. Emanations undou 
ly Cage from the bodies of females at certain pe- 
riods, which produce a lively impression on the sensa- 
tions of the male, and we should be inclined to admit 
that there might be some analogous concomitant of the 
luminous exhibition of the female glow-worm ; but the 
probability of this hypothesis is greatly diminished, on . 
considering, that the emanations of light belong to the 
earliest period, even when the insect is in the larva 
state. We must therefore necessarily conclude, that 
naturalists have not yet discovered the real uses of 
this remarkable property 
See Bartholinus de luce Animalium; Philosophical 
Transactions, vol. vi. p. 2178; vol. xv. p. 841; De Geer, 
Memoires sur les Insectes, tom. iv. p.29; Aldrovandus, 
De Inseclis, p. 494; Geoffroy, Mem. sur les Insect. 
tom. i. p. 166. () , 
GLUCKSTADT, a word signifying the Fortunate 
Town, is a town of Germany, in the Duchy of Hol- 
stein, and belonging to the King of Denmark. The 
town, which is situated on the Elbe, where it receives 
a small river called the Rhu, is regularly and neatly 
built; and the principal streets run into the market- 
place. The town is intersected by several canals, the 
principal one of which passes near the market-place, 
and is there joined by another, which divides the town 
into two parts. From the marshy nature of the sur- 
rounding country, the road from the town towards 
Krempe, passes over a stone causeway, nearly: three. 
quarters of a mile long. The town, therefore, can be 
easily laid under water on the land side. As there are 
no springs here, every good house is provided with a 
cistern, and the poor are supplied with water from the 
harbour in the new moat. There is a free grammar 
school here, a Calvinist church, a Roman Catholi¢ cha~ 
pel, and a Jewish synagogue. 
The foundations of this town were laid in a waste 
called the Wilderness, in 1617, by King Christian IV. > 
who, with the view of making it a commercial town, 
granted it particular privileges. Frederick III. in- 
creased these privileges, and made it the entrepot of 
all the merchandize of Iceland which came into the 
Elbe. The vessels of Gluckstadt carried their merchan- 
dize to Altona and Hamburg. In 1738, Christian VI. 
founded a commercial college here; and in 1739 a house 
of correction and a workhouse were founded, In 1750s 
1 
