HA RD WICKE'S SCIENCE- G OSSIP. 



135 



them. Microscopic examination revealed numerous 

 micrococci. These were cultivated and injected into 

 rabbits with negative results, but an acid watery 

 extract was obtained from the cheese, and from this 

 a precipitate that was soluble in ether. This solution 

 on evaporation gave crystals which were found, when 

 taken by men, to produce the symptoms above 

 described. It was therefore the poison, and has 

 received the name of tyrotoxican. The "Journal of 

 the Chemical Society " of April last, from which I 

 obtain these particulars, says nothing about the 

 origin of the cheeses. The locality suggests a sus- 

 pcion. American ingenuity has devised a method 

 oj obtaining both butter and rich fat cheese from the 

 s;me milk plus a cheap ingredient. The cream is 

 tiken from the milk, and the curd precipitated from 

 tie skimmed milk. Ordinary skim-milk cheese is 

 \ery hard, dry and unsaleable ; but these defects have 

 teen remedied by intimately mixing with the curd an 

 jmount of hog's lard sufficient to represent the 

 tbstracted butter. Query : Were these poisonous 

 theeses samples of this peculiar mode of manufacture ? 



The Evolution of Grasses.— A very interesting 

 paper was read at the Geologists' Association by 

 |. Starkie Gardner on this subject. The present pre- 

 ponderance of grasses over all other forms of vegetation 

 B very remarkable. There are over 3000 species, 

 estimated to occupy, under cultivation, one third of 

 lurope. Into this country alone their products are 

 imported to the value of nearly one hundred millions 

 st'rling. About 95 per cent, of the plants growing in 

 oldinary meadow land are grasses. Mr. Gardner 

 ccncludes that there was no great development of 

 gnsses until towards the close of the Eocene, no 

 definite remains having been found associated with 

 tht older Eocene floras of temperate latitudes, as 

 th«y should be had they then existed in any abun- 

 dance. The later deposits, such as the Miocene beds 

 throughout Europe, are crowded with them. In 

 further support of this conclusion, it was shown that 

 the teeth of all the early Eocene herbivorous 

 Mammalia were adapted for crunching fruits, snap- 

 pingtwigs, and grubbing up roots, rather than brows- 

 ing qi such food as grass. The geological history of 

 insecis was also put in evidence to support the theory 

 of the post mid-Eocene date of grass. The remains 

 of grais in the Tertiary deposits of Spitzbergen may 

 be older, but their age has not yet been accurately 

 correlated. These conclusions, if confirmed, indicate 

 a very distinctly marked epoch in the evolution of 

 both vegetable and animal life, as the introduction 

 of such an aggressive type must have altered the 

 charactei of both flora and fauna of the Temperate 

 Zones to an extent quite equal to that which the 

 other geologists attributed to violent catastrophes. 



Magic Uirrors. — Professors W. E. Ayrton and 

 John Terry have accidentally discovered that the 



amalgamation of metals is accompanied with great 

 expansive force. If one side of a thick straight brass 

 bar be amalgamated, this side becomes convex, and 

 the opposite side concave. They suppose that the 

 Japanese magic mirrors which have excited so much 

 controversy may be explained by an action of this 

 kind. These mirrors are made of bronze, are polished 

 on one side, and have raised figures on the other, the 

 polished reflecting surface appearing perfectly smooth 

 and regular, without any trace or indication of the 

 figures, yet when light is reflected from this surface 

 and thrown upon a screen the luminous image of the 

 mirror displays the figures that stand out on the back. 

 In a paper read some time ago before the Royal 

 Society, Messrs. Ayrton and Perry have already shown 

 that this magic result is due to the polished side- 

 opposite to the thinner parts of the casting being 

 more convex than that opposite to the raised parts, a 

 conclusion' they have verified by showing the reversal 

 of the pattern when formed by a convergent beam of 

 light. This would be the condition of such a casting 

 if the whole of the reflecting surface were subject to 

 an uniform expansive stress, as the thinner or weaker 

 parts would thereby become less concave or more 

 convex than the thicker parts. The authors now 

 suppose that, instead of this irregularity being pro- 

 duced intentionally in the course of manufacture, it 

 may have arisen accidentally from the use of a 

 mercury amalgam in the polishing of the reflecting 

 surface of the mirror. 



Arctic Ground Ice. — " The Popular Science 

 Monthly " states some facts indicating that the depth 

 of frozen soil in Arctic America is much greater than 

 is usually supposed. In 1SS3 Lieutenant P. II. Ray, 

 U.S.A., sank a pit near Point Barrow to a depth of 

 3S feet. At 28 feet from the surface the temperature 

 of the soil was 12 Fahr., and the same at 3S feet. 

 Taking the unit of increase of temperature per unit of 

 depth as i° Fahr. to 64 feet, he computed the total 

 thickness of ice at about 1300 feet. The depth to 

 which the summer thaw extends, and its rate of 

 progress, are more variable, as they depend more on 

 the season and exposure than does the depth of frozen 

 soil. In some respects the frozen substratum may be 

 advantageous, as it moderates the effect of the scorch- 

 ing heat of continuous Arctic sunshine, and supplies- 

 moisture to the roots of cereals when they most 

 require it. This is so much the case that General 

 Lefroy, who has studied the subject in Siberia, 

 believes that agricultural experience in the north- 

 west would be in favour of retaining the frozen ice- 

 even if it were possible to get rid of it. 



Arctic Summers. — There are few subjects con- 

 cerning which popular delusions are more generally 

 diffused than that of Arctic climate. The very name 

 of "the Arctic Regions " is so firmly associated in 

 our minds with ice and snow, polar bears, and 



