368 
POPULAE SCIENCE EEVIEW. 
utilization of sewage as already proposed, and there is every credit due to Dr. 
Cobbold for being the first to call attention to it. Some tbne ago Dr. John 
Harley discovered that one of the most formidable entozoa with which we are 
acquainted, the Bilharzia, had been introduced into this country by some 
colonists who had returned from the Cape of Good Hope. Now this Billiarzia 
is an awfully destructive entozoon, and commits dreadful havoc among the 
Egyptians : out of 363 post-mortem examinations conducted in Egypt by 
Dr. Griesinger, this parasite was found in 117 cases. It usually takes up its 
habitation in the blood-vessels, and gives rise to most painful symptoms, fol- 
lowed in the more advanced cases by extreme prostration and death. We say 
it has been introduced into England ; happily it has not spread over the 
country ; but, writes Dr. Cobbold, “ once let this distribution commence as a 
consequence of egg-dispersion on any extended scale, and I know of nothing 
calculated to prevent the rapid spread of the endemic amongst us. Such a 
scourge would add yet another serious local ill to the already formidable list 
of evils to which our British flesh is heir.” We do not think that Dr. Cob- 
bold’s exhortation is likely to prevent the utilization of the sewage, but at all 
events it may lead to the adoption of some means by which the ova may be 
destroyed while in the tanks. 
ASTRONOMY. 
Orbit of Sirius. — Mr. Auwers has recalculated the elements of the orbit 
of this remarkable star, which is now more interesting even than it was 
previously. He finds for its time of revolution round the hypothetical com- 
panion a period of about fifty years, moving at the rate of degrees per 
annum. Its passage through its lower apsis occurred in 1794. Assuming' 
the mass of the companion to be nearly one-half that of the principal star, 
he finds that at the present time the distance of Sirius from the common 
centre of gravity of the binary system is about 3^ seconds. Comparing his 
deductions with the places of the companion of Sirius discovered by Clark, 
the diminution of the angle of position of the large star is very perceptible, 
and agrees well ; but those of the observed distances are more doubtful, as 
might be expected. In one observation by Mr. LasseU, the distance is given 
as less than five seconds ; but in a subsequent one he is in agreement with 
the eight other observers. The difficulty of the measurement between the 
brightest star in the heavens and one of the faintest hidden in its rays, may 
easily be conceived ; but the present observations prove the truth of Sir J . 
Herschel’s remark, that the angles of position are more to be relied upon, 
than the measures of distance. 
Diameter of Sirius . — The incongruous results attending the measurements 
of the diameters of stars has long been a subject of complaint, and it is yet 
doubtful whether any probable approximation can be arrived at. Sir W . 
Herschel made use of mists and fogs in order to dimmish the intensity of 
their light, and thus concluded that the diameter of Arcturus was about 
one-tenth of a second. By a more artistic arrangement, M. Chacornac has. 
reduced the diameter of Sirius to an almost imperceptible point ; for with 
the highest powers this star does not appear larger than a star of the twelfth 
