2:;o 



THE POPULAR SCIENCE MONTHLY. 



mass of the population have to deny them- 

 selves this wholesome form of nutriment. 

 The London Society of Arts has under- 

 taken the investigation of the question of 

 fruit-growing, and is laboring to awaken a 

 popular interest in the matter. In this 

 country fruit is cheap and abundant, yet 

 many of the suggestions made on the other 

 side of the Atlantic would not be out of 

 place even here. In one of the papers read 

 before the Society of Arts, it is stated that 

 only 40,000 acres of land are set apart in 

 England for market-gardens. Considering 

 what enormous crops of fruit are obtained 

 from this inconsiderable acreage, how shall 

 we estimate the product of waste lands 

 were they to be cultivated ? The market- 

 gardens, as we have seen, cover less than 60 

 square miles ; but the railway embankments 

 represent about 200 square miles of land, 

 one-third of which, at least, could be used 

 for the cultivation of fruit. The little plots 

 of ground attached to cottages in the country 

 and in villages and suburban districts might 

 also be utilized for fruit-growing. Road- 

 sides in the country might also be cultivated 

 profitably. The prospect of success in this 

 effort at enlarging the area of fruit-culture 

 in England is not very encouraging, owing 

 to the unthriftiness of the people. In this 

 respect they compare very unfavorably with 

 their neighbors, the French. 



Frequency of Color-Blindness. There is 

 some reason for believing that writers on 

 " color-blindness " have in many instances 

 exaggerated with regard to the frequency 

 of its occurrence. Thus it has been stated 

 as a fact that no less than ten per cent, of 

 the railroad engine-drivers in Sweden are 

 unable to announce properly the color of 

 the signal-lamps, owing to color-blindness. 

 Mr. Herbert W. Page, surgeon to the Lon- 

 don and Northwestern Railway, is of the opin- 

 ion that, so far from being common, this af- 

 fection is extremely rare. He cites the tes- 

 timony of three railway examining surgeons 

 in support of his views. One of these, who 

 in the course of twenty-five years had exam- 

 ined many hundreds of men, writes that 

 color-blindness " is of excessive rarity ; " an- 

 other " has not found it common ; " while a 

 third, a surgeon of long experience, writes 

 that he has met with " oulv three cases of 



well-marked color-blindness " among many 

 hundreds examined by him. In 800 men 

 examined by Mr. Page himself, not one in- 

 stance of true color-blindness was found. 

 Similar testimony is given by Dr. Macaldin, 

 of the Midland Railway. 



How, then, are we to account for the 

 positive statements of other writers who 

 assert the extreme frequency of this affec- 

 tion ? In very many cases ignorance of 

 the names of colors is, doubtless, mistaken 

 for inability to distinguish between colors 

 themselves. Then, many persons are hesi- 

 tating and slow in their recognition of col- 

 ors. " Green may be spoken of as blue by 

 one, red as green by another, and the name 

 persisted in till the man be asked to com- 

 pare the one before him with some familiar 

 color, as the grass or sky, when his mis- 

 take will be recognized at once. I cannot 

 help thinking," adds Mr. Page, " that such 

 cases as these have often been mistaken as 

 instances of color-blindness. It certainly 

 is within my own experience, that errors of 

 this kind may creep in unawares unless time 

 and care he given to the examination of those 

 who are ignorant^ stupid, or nervous." 



Marsh-Fevers. A substantial addition 

 to our knowledge of the true nature of pa- 

 ludic fevers appears to have been made by 

 Messrs. Lanzi and Terrigi, of Rome. Lanzi 

 has found in the cells of microscopic algae 

 from the Roman marshes certain dark-green 

 granules, which are most numerous when 

 the plants are farthest gone in decomposi- 

 tion. At length these granules fill the cells, 

 are black under the microscope, and the 

 algae emit an offensive odor. In the Cam- 

 pagna marshes are formed in winter, which 

 in spring develop algae abundantly. In 

 summer the water disappears, and the algae 

 then putrefy, the ground afterward growing 

 phanerogamous plants. Toward the fall of 

 the year the algae in the parts still covered 

 with water also die, and the slime at the 

 bottom of the marshes contains quantities 

 of the dark granules. The latter may also 

 arise from other plants in the state of decay, 

 even where there are no marshes. Lanzi 

 regards these granules as a sort of ferments. 

 Now, the pigment-granules found in the liv- 

 er and spleen of individuals suffering from 

 malaria have quite similar properties to 



