HARDWICKE'S SCIENCE-GOSSIP. 



31 



ticularly. We do not known any other manual which 

 so clearly and succinctly deals with the Theory 

 of Sound, in its various departments. 



The Electric Light Popularly Explained, by A. 

 JBromley Holmes (London : Bembrose & Sons). 

 This cheap, little, well-written, and easily-understood 

 brochure ought to be in every house in England, and 

 read by every intelligent resident. (Fifth edition.) 



Our Fancy Pigeons, by George Ure (London : 

 Elliot Stock). This is an interestingly-written record 

 of fifty years' experiences in pigeon breeding, and the 

 ^author is a genial and observant naturalist besides. 

 Mr. Ure's name as an authority upon the subject of 

 this book is sufficient to command for it a large 

 circulation. 



Metal Turning (London: Whittaker & Co.). 

 One of a valuable series of cheap and practical 

 manuals, well and abundantly illustrated, which will 

 considerably help on the all-important subject of 

 Technical education. It is written by " A Foreman 

 Pattern-Maker," and tells and explains and illustrates 

 to the reader all the particulars of the Lathe, and its 

 various tools. 



Electro j\Iotors, by S. R. Bottone (London : 

 Whittaker & Co.). Another of the same series. 

 Mr. Bottone has been in the front of popular and 

 practical teachers and writers on electro-dynamos for 

 ten years past. The brightly got up little manual 

 before us has been prepared by him specially for 

 amateurs as well as practical men. 



l\Iagnetistn and Electricity, by J. Spencer (London : 

 Percival & Co.). Another addition to the numerous 

 "manuals " written for the over-manualised students 

 of South Kensington, who exist and are tortured for 

 the benefit of "The Department." Mr. Spencer's 

 book is a good one, nevertheless ; although we always 

 feel sorry for the over-written "students of South 

 Kensington," wherever they may be. 



Sound, Light, and Heat, by J. Spencer (London : 

 Percival & Co.). Another "iclass-book " for 

 -students of South Kensington in the elementary 

 stage. It is of course a good little book, and is 

 written by a man who knows how to teach, and 

 something of the people who have to be taught. 



The Dai-winian Theory of the Origin of Species, by 

 Francis P. Pascoe (London : Gurney & Jackson). 

 Mr. Pascoe is one of the best literary naturalists of 

 ithe day, and anything he has to say on subjects like 

 .those discussed in this pleasant little book is bound to 

 ibe listened to. Mr. Pascoe dwells particularly on the 

 fact (which we have been for years maintaining) that 

 Darwinism and evolution are not identical. The 

 former is a minor, the latter is a major term. Darwin 

 discovered and propounded the Doctrine of Natural 

 selection, and many of his too-ardent followers 

 imagined that was sufficient to settle all biological 

 •difficulties. But Darwin himself knew better, for he 

 grafted the theory of Sexual Selection upon it. The 

 fact is. Evolution includes not only natural selection. 



and sexual selection, but perhaps a hundred, a 

 thousand, other active and operative agencies 

 besides. We cordially recommend Mr. Pascoe's 

 book as a valuable contribution to the literature _of 

 evoiutidn. 



A FEW NOTES CONCERNING COCHINEAL. 

 {COCCUS CACTI.) 



By H. DURRANT. 



THIS insect which we use as a dye was supposed, 

 previous to about 1714, to be some kind of a 

 seed, although it was said by Acosta, as early as 1530, 

 to be an insect. However, its real nature is now 

 placed beyond doubt. Mexico is the real home of 

 the cochineal, but it is also cultivated in Teneriffe and 

 several other places. The cochineal we get is about 

 as large as a peppercorn, shrivelled, and of a dark, 

 purplish colour, ovate, convex and transversely 

 furrowed above, smooth beneath. Externally it 

 appears covered with a fine white powder, but when 

 the insect is examined under the microscope, this is 

 resolved into fine hair. 



The males do not enjoy a very long spell of life, 

 generally dying when about a month old. Their 

 wings are perfectly white. The females are the only 

 ones of any value, from a commercial point of view. 

 When they have selected the leaf which is to serve 

 them as a habitation, they fix themselves to a leaf by 

 their proboscis and never leave it. There are two 

 varieties of cochineal : the wild kind, called by the 

 Spaniards Grana sylvestra, and the cultivated variety, 

 or Grana fina, which] is greatly superior to the former 

 in regard to the furnishing of colouring matter. 



The wild kind is much more downy, though uot so 

 large as the cultivated insect, but by cultivation it 

 becomes larger, and loses much of its woolly 

 appearance. 



The cochineal feeds on several species of cactus, 

 principally Cactus cochinellifer and Opuntia cochiw 

 illifera (Nopal cactus). It does ^not, as formerly 

 supposed, derive its colour from the juice of the plant 

 on which it feeds, whose flowers are red, because the 

 insect can be reared upon different species of Opuntia 

 whose flowers are not red. 



One of them {Opuntia cochiitillifera) is cultivated 

 for the purpose in Honduras and Mexico. When the 

 time arrives for the insects to be collected, they are 

 brushed off the trees with the tail of an animal, into 

 bags, and killed by immersing in boiling water. 

 They are then taken out and dried thoroughly in the 

 sun, and put up in serons, or skin bags, for 

 exportation. 



The qualities of a good insect, when dried, should 

 be that they are plump and dry. If they are small 

 and have a pink tinge they are least esteemed. The 

 colouring matter of cochineal is carminium, and was 

 first extracted by Pelletier and Caventon by digesting 



