It is stated in the Chemical Review that recent analyses of the water from the Holy Well at Mecca, which is so eagerly drunk by pilgrims, show this water to be sewage, about ten times stronger than average London sewage.
HOW TO ESTABLISH A TRUE MERIDIAN.
In looking over the excellent article of Professor S. M. Haupt, in the SCIENTIFIC AMERICAN SUPPLEMENT, No. 360, on the subject of finding the meridian, I discovered that one important step is not given, which, might prove an embarrassment to a new beginner.
In the fourth paragraph, in the third column of page 5,748, he says: "Having now found the altitude, correct it for refraction, ... and the result will be the latitude."
It will be observed that this result is only the true altitude of the star. The latitude is found by further increasing or diminishing this altitude by the polar distance of the star.
This paper will be of great value to engineers and surveyors, for the elementary works on surveying have not treated the subject clearly.
H. C. PEARSONS, C.E.