556 



SCIENCE. 



[N. S. Vol. II. No. 43. 



upon the cornea, it was evident that the whole 

 phenomenon, gas light included, was in my eye 

 so far as sight was concerned. In short, since, 

 when a movement of the lower lid lengthens or 

 shortens the ' rays ' which appear to shoot up- 

 ward toward the ceiling, and a movement of 

 the upper lid vice versa, one can see that the 

 image in his eye is inverted, because the sides 

 of this cone and the background of the room 

 are reversed. 



If one will work this experiment to the point 

 of perceiving that the picture of the outside 

 world is entirely in his eye, he may come, as I 

 did, to the fearful demonstration that even in 

 ' full light ' outside of his eye all is in a eertaiu 

 sense total darkness. It is a dreadful momen- 

 tary concept, more dejecting than the fear 

 which attends the coming on of blindness from 

 destroyed vision. J. B. Woodworth. 



Cajibkidge, Mass., October 12, 1895. 



It follows from Mr. Woodworth' s observation 

 that the image on the retina is inverted. The 

 'rays of light' are not, of course, objective, but 

 are due to imperfect accommodation. The light 

 from a gas jet passing through the lower half of 

 the pupil is in part refracted do-miward, affects 

 the lower half of the retina, and is projected as 

 rays extending upward. The same inference 

 can be drawn from an examination of Purkinje's 

 figures (the blood vessels of the retina), subjec- 

 tively and objectively; or, indeed, by pushing 

 the eyeball upward, in which case objects seem 

 to move downward. 



It is commonly believed that the external 

 world sends up through the nerves little images 

 of itself which are examined by the mind. This 

 seems to the present writer a 'dejecting con- 

 cept.' Per contra, the fact that the world in 

 which we live is a mental construction assigns 

 to mind its due place in the universe. 



J. McK. C. 



' CRYING WITH TWO EARS. ' 



In Science for October 11th (page 487), Pro- 

 fessor J. McK. C, corrects an inaccuracy in 

 Professor Brooks' statement concerning the in- 

 verted image. He closes his criticism with the 

 paragraph: " A similar paradox is the fact that 

 with two images on the retinas we see things 

 singly. This may also be treated without undue 



seriousness by the question: ' If we hear a baby 

 crying with two ears, why do we not think it is 

 twins? ' " What terrible sort of baby is it that 

 cries with two ears ? I protest against such a 

 little monster. Is it not sufficient that a baby 

 cry with one throat, and that we hear it with 

 two ears? And are there not times when we 

 think it is triplets? W. H. Fishburn. 



Second Presbyterian Church, 



CoLUJEBrs, 0., October 12th, 1895. 



inaccurate zoology. 

 The Editor of Science — Sir : It appears to 

 me that zoologists should endeavor, whether 

 for their own good or that of the science they 

 cultivate, to see that popular zoological works 

 are prepared by zoologists, instead of being 

 compiled by persons comparatively ignorant oi 

 the subject. Perhaps the most effectual means 

 to this end consists in pointing out the inaccu- 

 racies of works which have not been written 

 vnth sufficient knowledge, so that the public 

 maj' be more careful about what it accepts. 

 No one appreciates more than the present 

 writer the great difficulty of ensuring perfect 

 accuracy, and it is not suggested that those who 

 might be criticised have not done the best in 

 their power ; the point is, rather, that the ser- 

 vices of specialists should in every case have 

 been secured. 



Even so, curious errors will sometimes ap- 

 pear ; perhaps usually due to the writer trying 

 to cover too much ground. Thus in the Stand- 

 ard Natural History there is a figure of a Ptil- 

 vinaria, called ' Coccus adonidum ;' this latter 

 name belonging really neither to a Coccus (as 

 now understood) nor a Pulvinaria, but a Dacty- 

 lopius ! 



A few days ago the new Standard Dictionary 

 of the English Language (Funk & Wagnalls Co., 

 1895) was received, and on looking over it I at 

 once stumbled on the following curious items : 

 (1.) The cotton scale-insect is ' a bark-louse 

 (Pulvinaria innumerabilis).' There is no 

 recognized cotton scale-insect in this coun- 

 try, though there are scale-insects which 

 affect cotton. Pulvinaria innumerabilis is 

 not a cotton species, but affects maples in 

 the North. Cottony scale is doubtless what 

 was intended. 



