398 



SCIENTIFIC NE^VS. 



[April 27, if 



cochineal, lac and kermes, contain a red fluid, of which 

 carminic acid appears to be the essential ingredient. 

 Carminic acid has also been found (by Sorby) in an 

 aphis of the apple-tree. If we ask what purpose this 

 red substance serves in the case of these few insects, 

 and why it is found in them alone, a partial answer 

 can be given. Kuhlmann showed some time ago that 

 cochineal has the same oxygen-carrying property as 

 haemoglobin. When added to a reducing agent, such as 

 ammonium sulphide, hydrated oxide of iron, or zinc and 

 sulphuric acid, it loses its colour, but regains it on shaking 

 up with air, and the process may be repeated indefi- 

 nitely. Now, haemoglobin itself occurs in one insect, 

 the aquatic larva of the gnat-like chironomus. A red 

 fluid, probably of respiratory function, exists therefore 

 in these insects, and so far as is known, in none beside.* 

 If we wish to clear up the function of what we are now 

 entitled to call the respiratory pigment of the scale- 

 insects, we must ascertain what the insects which possess 

 it have in common as to mode of life, and look out for 

 some peculiar habit, or environment, which demands an 

 oxygen-carrier in their lymph. Some time ago. Scien- 

 tific News, Vol. i., p. 129 (first series), we pointed out, 

 by means of a general survey of the animal kingdom, 

 that an oxygen-carrier is specially required by animals 

 which havea limited respiratory surface, and among others, 

 by such as dwell in burrows or confined situations. Now, 

 chironomus is a tube-dweller, living in a burrow made 

 by itself out of vegetable refuse. The scale-insects are 

 protected as larvae either beneath the body of the 

 mother or in a house, cell, or nest made by her. As 

 adults their body is dense, and mainly serves as a 

 roof to the young brood. The difficulty of getting a 

 good supply of air to the internal tissues of the body 

 which these conditions seem likely to occasion, is in- 

 dependently evinced by the fact, long ago established by 

 Leydig, that scale-insects possess two pairs of long air- 

 tubes, which project beyond the walls of their tem- 

 porary habitation. So far all is consistent, and we can 

 give some shadow of a reason why chironomus and 

 certain scale-insects should differ from other insects, and 

 resemble the earthworm, as well as nearly all verte- 

 brates, in the possession of a respiratory pigment. The 

 aphis of the apple-tree still remains unexplained. As 

 to this insect and its mode of life, adequate information 

 is not accessible to us. But the analogy of other forms 

 of life renders it hardly unsafe to conjecture that when 

 its natural history is fully cleared up, we shall find that 

 this too, by reason possibly of some obstruction to free 

 breathing over the whole surface of its body, stands in 

 special need of the respiratory pigment which it 

 undoubtedly possesses. It is to the parasitic and seden- 

 tary habits of the scale-insects that we owe the proper- 

 ties which make certain of them commercially valuable, 

 and it is worth while to study our unproductive and 

 noxious native species, if only to understand a little 

 better how the red dyes of cochineal, lac and kermes, 

 the insect wax of China, and the shellac of which we 

 make sealing-wax, marine glue and lacquer, are severally 

 produced. 



Action of Forests on Rainfall. — Mr. Ganett, 

 writing in Science, maintains that neither planting nor 

 denudation exerts any constant influence upon rainfall. 



* The head of the housefly contains a red fluid, which is Relieved 

 net to be haemoglobin, nor to contain carminic acid. 



THE LICK OBSERVATORY OF THE 

 UNIVERSITY OF CALIFORNIA.— II. 



(^Concluded from page 364.) 



IT is interesting to compare this telescope with the 

 simple instrument made by Galileo in 1609, consisting 

 of a single leaden tube with a plano-convex lens at one 

 end for an object-glass, and a plano-concave lens at the 

 other end for an eye-piece, and magnifying three times. 

 Ever since Galileo's brilliant discoveries with this " optick 

 tube," described by Milton in his visit to Padua, the 

 growth of the telescope has been of steady progress, in 

 spite of the opinion of a contemporary profession of 

 Galileo in the University of Padua, who argued that 

 things invisible to the naked eye are useless and do not 

 exist." In tracing its development briefly we find that 

 the difficulties in obtaining good glass led Newton to con- 

 struct a reflecting telescope in 16S8, which magnified 

 thirty-nine times, the speculum or mirror being made of 

 an alloy of copper and tin. Improvements followed, 

 which finally resulted in Herschell's finely-constructed 

 instruments, in the large six-foot reflector in its gigantic 

 frame, made by Lord Rosse, and in the celebrated re- 

 flectors of the present time. The reflecting continued to 

 supplant the refracting telescope until about 1753, when 

 Dolland, an English optician, showed that lenses of flint 

 and crown glass could be combined in such a manner 

 that their dispersive powers would neutralise each other, 

 and this is the principle of construction of the achromatic 

 objective now in use, consisting of an outer double convex 

 lens of crown glass and an inner lens nearly plano- 

 concave of flint glass. 



The twelve-inch refractor, which was originally made 

 for Dr. Henry Draper's private observatory at Hastings, 

 N.Y., by Alvan Clark and Sons, is of the finest con- 

 struction. The object-glass of the 6g-inch equatorial was 

 also made by the Clarks, and is provided with a port- 

 able mounting, made by Warner and Swasey. The 

 four-inch comet-seeker, made by Alvan Clark and Sons, 

 has a focal length of thirty-three inches. 



The photoheliograph is mounted south of the transit 

 house. The transit instrument determines the axis of 

 the photoheliograph, and this is also used as a collimator 

 for the transit. The six-inch Repsold meridian circle 

 was delivered in 1884, after having been inspected by 

 Professors Auwers and Krueger, of Berlin. The declino- 

 graph was made under the supervision of Dr. Johann 

 Palisa, of Vienna, to fit either a twelve-inch or six-inch 

 equatorial. The universal instrument marie by Repsold 

 consists of a telescope containing a prism, into which the 

 rays of light are reflected. Its aperture is 2'i5 inch. 

 The horizontal circle reads by two microscopes to 2", 

 and the circles are ten inches in diameter. This is a 

 perfect geodetic instrument, and, together with a six- 

 inch equatorial and a chronometer, can be easily packed 

 for astronomical expeditions. There are several chrono- 

 meters made by Negus, and a thermometric chronometer 

 by C. Frodsham. The most important of the minor in- 

 struments are the filar micrometer for the thirty-six inch 

 telescope by Fauth and Co., the duplex micrometer by 

 Grubb, and a star spectroscope made by Brashear, from 

 Mr. Keeler's designs. Plans for a large solar spectro- 

 scope are being worked out by Professor Holden and 

 Professor Langley. The other instruments are a deli- 

 cate sphereometer by Fauth and Co.; resistance coils ; 

 galvanometers; a disk photometer; spectroscopes ; a 

 lever-tester of refined construction ; and an engine for 



